What is an alternative to chicken broth for Mexican rice?

Some recipes might be pickier, but Mexican rice is almost certainly the kind of thing where the broth is just there to add a bit of background flavor, and it doesn't have to be specifically chicken. So you can be pretty flexible. Your primary options are:

• Use a different kind of pre-made broth. They'll all work for something like that, just provide slightly different flavors.
• Use bouillon cubes/paste. These are likely to be less expensive since they don't have all that water weight/volume that costs money to ship. You can even buy them online, depending where you live. They do tend to be saltier, so be careful - if the recipe calls for any other salt, you can probably just leave it out.
• Make your own. If broth is expensive but you can get a whole chicken you'll be in fine shape. And again, not-chicken is fine too; you can use any other kind of meat with plenty of bone in it. If you go to a little trouble, you can get something way, way better than you'd ever buy. (Just search online for recipes; there's no shortage.) But even just boiling a whole chicken in water will get you something usable.

And if somehow none of that works... water, a little seasoning (something with some umami in it) and salt if necessary? Water plus some kind of instant seasoning packet, even ramen seasoning? It's hard to say, since I don't live where you do and know what's easy to find.

Chicken Ramen packets work great, just add a little bit of cumin and garlic in some form.

When in Mexico we don't have chicken broth for cooking rice or whatever we use «caldo de pollo la suiza (Knorr brand)» and water. This brand is THE ONE WE LIKE IN MEXICO. The others are not that good.

I am finding lately that rice cooked with water rather than any broth is allowing the taste of the rice to come through. I prefer jasmine rice as my staple rice. The last two batches I made - one with chicken broth and one with water - settled it for me. The batch with chicken broth had none of the pleasant flavors associated with jasmine rice. Instead, all I could taste was chicken flavor (the broth was low sodium and fat-free, so no issues there).

If you are using more strongly-flavored rice, like wild rice, the flavor should not be overpowered by the broth. But still, if you are insisting on using quality ingredients (esp. the rice in a Mexican rice dish), you may want to avoid masking the natural flavor you would get otherwise.