As is known, during Sefiras HaOmer, you should not say "today is x day of the Omer" (or similar) before counting sefirah in Maariv, as this would prevent you from counting with a bracha later (Shulchan Aruch OC 489:4, HT DoubleAA). This is why people commonly say "what was last night's sefirah?" or the Gabbai announces in shul "last night's sefurah was ".
Does saying the words "Lag Baomer" or "it's Lag Baomer, I'm so excited" or some such, count as counting?
The Mishna Berura (489 sk 22) posits that if you don't say the number of weeks (on a night where there are weeks to count) in response to a friend then you may continue to count with a bracha later that night.
This is a combination of a number of considerations. First, there is a machloket if the weeks count is an absolute requirement (l'ikuva) on every day, or only on the full weeks (days 7, 14, 21 etc.). There is also a machloket if one needs to intend to fulfill the mitzva in order to fulfill the mitzva. The Mishna Berura rules that even if we think like the opinion who holds that weeks are not integral on the middle days, one still may have had to intend to fulfill the mitzva. Thus if one answered only the days and did not intend to fulfill the mitzva, he may continue and say a bracha that night.
He finally notes that for us, who always count with the weeks in a very set nussach, the very fact that someone left out the weeks shows that he was not intending to fulfill the mitzva, and can possibly even function as 'negative kavana' guaranteeing the permissiblity of continuing to recite a blessing later that night.
From Halachically Speaking, Volume 3 Issue 16:
Some poskim say one who has not yet counted the sefira of Lag B’omer should avoid telling someone else today is Lag B’omer, since doing so may be considered counting the day.78 Other poskim permit this since his intention is not to count the day, rather he is referring to the name of the day since it is a day of simcha.79 This seems to be the minhag ha’olom.
78: Refer to Shulchan Aruch 489:4, Biur Halacha 489 “sh’im,” Lag B’omer page 176.
79: Ohr L’tzyion 3:16:4:footnote 4, Avnei Yushfei 5:75:5.
