Do you need a pass port to go to Monterrey Mexico from Texas?

If you are going in an airplane, you do. If you are going by land (bus, car) you need your birth certificate and picture ID. Beginning in 2008, you will need your passport by air and by land. But right now, you only need the passport if you are flying. Have fun! Monterrey is GREAT!

you do now

Yes, even Mexicans in the US have to have passports to re-enter Mexico from any border in the US now. The post office in my area has so many people (Hispanic & US citizens alike) applying for passports that I can't even find a parking space, let alone get in to mail a package! It's driving me nutz!! Also, for 18 years I've been crossing the border into Ontario Canada to see my sister with just a birth certificate and a drivers license, now I have to pay 98.00 for a passport to see her again. It really sucks, but that is the price we pay to help guard against terrorist entry.

yes

At this moment (May 2007) if you do not go by air, you do not need a passport (I'm assuming you are a US citizen). If you fly, however, you will need one. For complete explanations of the rules, the US and Mexican government websites are your best sources of information.

As the US State Department writes on their site:

"Beginning January 23, 2007, ALL persons, including U.S. citizens, traveling by air between the United States and Canada, Mexico, Central and South America, the Caribbean, and Bermuda will be required to present a valid passport, Air NEXUS card, or U.S. Coast Guard Merchant Mariner Document, or an Alien Registration Card, Form I-551, if applicable.

"As early as January 1, 2008, ALL persons, including U.S. citizens, traveling between the U.S. and Canada, Mexico, Central and South America, the Caribbean, and Bermuda by land or sea (including ferries), may be required to present a valid passport or other documents as determined by the Department of Homeland Security. While recent legislative changes permit a later deadline, the Departments of State and Homeland Security are working to meet all requirements as soon as possible. Ample advance notice will be provided to enable the public to obtain passports or passport cards for land/sea entries. "

i'm not sure but it would be a good idea to take it.