Yes, those documents are enough to cross back to the U.S. However, when you go to Mexico they might ask you for your passport and if you don't have it they might return you back to the US, let you in, or ask you to pay something
Yes. You do not need a passport unless you plan on being pulled over/cited in Mexico. You can cross back into the US with just a birth certificate and/or drivers license, though you will need to use the slower 'all traffic' lanes when returning.
No, you need a passport
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