We've had such a hard time with this! My dh is from Mexico, born & raised there. Every time we go to visit my inlaws or they come here, we try to get books, and it's next to impossible! Nobody knows what I mean or what I want. At least in my dh's city, parents must not read to their kids like we do here, at least not as often or as much because it's so hard to find kids' books.
We've gotten some from friends and online that are common books here, and that's ok with me because it's better than nothing. We have goodnight moon (buenas noches luna), brown bear brown bear (oso pardo oso pardo que ves ahi?). We have a bunch of sesame street ones. Recently I bought online a book called "Tortillas para mama" that has traditional rhymes in Spanish and English. Although my dh and mil were only familiar with a couple of them, it's still nice to have.
If you find anything you really like, let us know!