Posting from Rio Grande, PR. Shavua Tov...
AMIGO supermarket is owned by WalMart -- lots of packaged kosher products you would find in the US (and many Great Value products with Hashgacha), cookies, crackers, pasta, pasta sauce, etc., etc.
In the Econo supermarket (same shopping center as WalMart), there were Toufayan kosher bagels, as well as several varieties of Pita from Toufayan -- whole wheat, regular, pocketless. There was also Kontos Pocketless Pita, as well as 'pizza crusts'
All the supermarkets also have a decent selection of Morningstar Farms and other manufacturers' vegetarian frozen products -- veggie burgers, chicken cutlets, hot dogs, sausages, etc.
A different kind of bagels were available in the AMIGO supermarket. ALL the supermarkets have soft tortillas from several manufacturers with a Hechsher -- almost all the soft tortillas (and there is a huge selection of them) are kosher, imported form the US, CRC, OU, and others.
Chalav Stam is available everywhere -- if you won't drink the local brands, there is lactaid and Skim Plus with OU
I'll update more as I find more....but so far, plenty to buy here at prices pretty similar to back home (if not cheaper in certain cases).