Sifre in English, Yale University Press, translated by Reuven Hammer.
Sefer Ha-Qabbalah by Avraham Ibn Daud, The Littman Library of Jewish Civilization, translated by Gerson D. Cohen
Mekilta de-Rabbi Ishmael, The JPS Library of Jewish Classics, translation by Jacob Z. Lauterbach
Tosefta, Hendrickson Publishers, translation by Jacob Neusner
Mekhilta deRebbi Shimon bar Yohaï, The Jewish Publication Society, translation by W. David Nelson
Seder Olam Rabbah, Jason Aronson, Inc. Publishers, edited by Heinrich W. Guggenheimer
Although this is not exactly the Brayta of 32 Rules, Rabbi Adin Even Yisroel Steinsaltz's English Reference Guide to the Talmud, Random House, has a section called "The Principles of Talmudic Hermeneutics" which covers that material in detail.
I recall there was an English translation of "The Letters of Rabbi Akiva" in the late 1960's or early 1970's. It might be found on EBay or a used bookstore.