Answer to question regarding benefiting from the fragrance of blossoms of an orlah tree:
The Radbaz (Shu"t 1:44) discusses this topic and rules that, if the tree was not planted for its fruits or if only the blossoms are present and the fruit has not yet grown, the fragrance is permitted (i.e. there is no problem of orlah preventing enjoyment of the fragrance):
כללא דמלתא אין לך דבר של ערלה שיהיה אסור להריח בו אלא אילן הנטוע לפירות מאכל ומריח בפירות עצמו אפילו בעודם בוסר ולא בעודם סמדר
The Chida (Birkei Yosef YD 294:13) agrees with this ruling. This topic is also discussed at length by Rabbi Pinchas Zabichi (Ateret Paz I, YD 16).
Since the almond tree to which you refer was presumably not planted with the intention that its fruits be eaten, the Radbaz would seemingly allow enjoying the fragrance (and, of course, reciting a blessing on the fragrance) even of the almonds themselves. If the almonds are still in blossom form, the Radbaz would allow enjoying the fragrance even if the almonds were of the edible variety and the tree was planted for its fruit.
Update for revised question regarding Birkas HaIlanos:1
1. The blessing may only be recited on trees of a type that grows edible fruit
R' Ya'akov Chagiz (Halachot K'tanot 2:28) writes that he demonstrated in Lechem HaPanim (his commentary on the Shulchan Aruch)2 that Birkas HaIlanos should only be recited on the blossoms3 of a tree whose type grows edible fruit:4
בפי' הש"ע הוכחתי... ושם מוכח דאין לברך אלא על אילני מאכל
As DoubleAA mentioned, the Mishna (Ma'aseros 1:4) indicates that a bitter variety of almonds, while generally inedible (consumption can lead to cyanide poisoning), is edible at some point before ripening. (Note: Although amygdalin and hydrogen cyanide levels have been shown to vary as bitter almonds ripen, modern varieties of bitter almonds may indeed be dangerous to consume whether ripe or unripe. Consult a doctor or botanist).
That said, I don't know whether the particular variety of almond you mention is the same as that discussed in the Mishna, but it sounds like it is not commonly consumed nowadays (particularly as food). CYLOR regarding whether the tree you mention is appropriate for Birkas haIlanos.5
2. Reciting the blessing over an orlah tree
R' Dov Berish Weidenfeld (Doveiv Meisharim 3:5) rules that the blessing may be recited over an orlah tree since the b'racha is not related to the future enjoyment of those specific fruits but rather to the fact that fruit bearing trees are experiencing their annual renewal in Creation (and this phenomenon ultimately allows people to enjoy eating fruit in general). R' Weidenfeld supplements his position with a number of arguments. The Tzitz Eliezer (15:15:1) agrees with R' Weidenfeld and, defending his arguments, rules accordingly. The Ben Ish Chai likewise permits reciting the blessing over an orlah tree (Rav P'alim III, OC §9).
However, see R' Akiva Eiger (OC 226) who is unsure whether a person may recite the blessing on a blossoming orlah tree (and who implicitly rules out of doubt that one may not recite the blessing). He writes that, if a person is unsure whether a tree in the Diaspora is orlah, he may recite the blessing, since safeik orlah in the Diaspora is permitted. Likewise, R' Malkiel Tzvi Tenenbaum (Divrei Malkiel 3:2) rules stringently against reciting the blessing (despite advancing a possible argument permitting it). R' Nissan Kaplan (Shalmei Nissan on chapter Keitzad M'varchin §79) suggests an argument permitting recitation, but ultimately is inconclusive due to the opinion of his father-in-law Rabbi Avraham Gurwitz that the critical factor is whether the fruits will be permitted to the observer.
Due to dispute over the matter, R' Ovadia Yosef (Yabia Omer vol. 5, OC §5), following the principle of safeik b'rachos l'hakeil (see for e.g. Shulchan Aruch OC 209:3), rules that the blessing should not be recited over orlah trees.
CYLOR regarding whether you should or may recite this blessing over trees that are still in the orlah stage.6
Unfortunately, this update comes just after the end of Nissan. However, we generally follow those poskim who allow the blessing to be recited at any point during the year (Machatzis HaShekel OC 226). Interestingly, R' Ya'akov Chagiz, one of the poskim who rules that the blessing may only be recited in Nissan, uses almonds as an example of a fruit tree that blossoms early and that therefore usually may not be used for the blessing (Halachot K'tanot 2:28, see also Rashi to Koheles 12:5: אילן של שקדים כלומר שתקפוץ הזקנה עליו כשקד זה הממהר להנץ לפני כל האילנות). Out of doubt, the Kaf HaChayim (OC 226:1) recommends that someone reciting the blessing not during Nissan should omit Shem u'Malchus.
2 Although R' Chagiz traveled to Constantinople intending to publish his manuscript of Lechem HaPanim, he passed away there, and the commentary is thought to be lost to posterity.
3 R' Chagiz writes that the blessing may be recited even after the petals fall off in the fruit set stage. There is a dispute among the poskim regarding whether the blessing may even be recited during the fruit enlargement stage (see Bi'ur HaGra OC 226:1 s.v. v'im, Mishna B'rura OC 226:4 for a survey of opinions; see also Bach OC 226:2 who suggests that the blessing may be recited if the person had not seen the blossom earlier). The Mishna B'rura indicates that it should not be recited once the fruit is mature.
4 The prevailing position is that the blessing may only be recited on trees of an edible-fruit bearing species (or, according to some opinions, on trees that actually bear edible fruit, see the contemporary book Ma'aseh Chemed by Rabbi Eliyahu Cohen). However, there are opinions that disagree. R' Ya'akov Emden writes that the blessing may be recited on non-fruit-bearing species (Mor uK'tzi'ah 225), R' Avraham miBuczacz (Eshel Avraham OC 226) is in doubt as to whether the blessing may be recited over them. Partially in consideration of R' Ya'akov Emden's opinion, the Shevet HaLevi (6:53:4) suggests that someone should not repeat the blessing if they already recited it on a species of tree that does not bear edible fruit.
5 Incidentally, R' Chagiz infers from the Rambam (Hil. B'rachos 10:13) that the blessing should only be recited when multiple fruit-bearing trees are observed in bloom. It is unclear why R' Chagiz thought that the language of the Rambam implies this any more than does the language of the gemara (B'rachos 43b). In any case, the Chida (Moreh b'Etzba ch. 7, §198) indicates that m'dakd'kim are particular to follow this practice.
6 For some contemporary internet rulings on the matter, see the opinions of: Rabbi Ya'akov Sasson (permitting), Rabbi David Lau (permitting), Rabbi Eliezer Melamed (permitting if there is no other alternative, but see here, where he seems to rule more stringently but mentions that the blessing may be recited unless the observer knows that the tree is orlah), and Rabbi Ya'akov Yehudah Zilberlicht (brings both sides, but perhaps seems inclined to permit).