Just to make sure, I went to Super Palengke Market on 1st Avenue just below 14th street (231 1st Ave.), and found that they have tapioca pearls in bags, presumably the ones used for making bubble tea. (I'm sure that New Manila Food Mart, over on 14th street near 1st, has the same thing for a competitive price as well.) Considering they're so cheap ($1.10 for a 14-oz. bag), it strengthens my resolve not to go to Saint's Alp; I'd rather buy the tea at Ten Ren's and make it at home, anyway.
They carry two sizes of the pearls: small and large. I'm guessing the small are the ones that are usually used, but I haven't tried cooking them yet. The large require an overnight pre-soak and probably end up as large as marbles; the English on the package is worth the price of admission alone: "The cooked tapioca pearls thus derived will be chewy and mat be served in various styles as desired."