Welcome to the fire new...couple, Wildman mentioned you'd be stopping by. If you rent a car be aware that your US insurancce doesn't work in Mexico. You'll need to buy Mexican insurance. Check with the rental agency or your travel agent.
Watch out for animals on the road.

If you are in an accident and someone gets hurt there is a good chance you'll end up in jail. They have a tendency to lock up everyone involved then settle the matter in court.

I travel to Mexico for work fairly often but I usually have a local driver to get me around. Even so, we've been stopped by cops seeking bribes four times out in my last five trips down there. I'm NOT in tourist areas though, your travels may be different. Luckily the few times I've driven myself I wasn't stopped. I'd rather get a taxi than drive myself, but then all my fares are rembursed by my company so if the driver overcharges me it doesn't really come out of my pocket.

Notify the US Consulate that you'll be in Mexico. There's a link somewhere on the webpage to do this. This speeds up response time if anything does happen. Keep copies of the nearest US consulate phone number in your wallet.

Speaking of wallets, notify your credit card companies that you'll be out of the country so that they'll be more aware of the possibility of fraud. This also will prevent what happened to my co-worker who had his cable company automatically charge his credit card. The bank saw a charges on the same day here in the US and also in Mexico, thought his card had been stolen and cancelled it without telling him, leaving him unable to pay for anything.

No knives WHAT SO EVER! Mexico is really touchy about Americans bringing in weapons and even a tiny Swiss Army Knife "Classic" can put you in jail if you get the wrong cop/judge.

There is much truth in the phrase, "Don't drink the water." Keeping some imodium AD on hand at all times is a good idea.

Spread your cash around your body. The less you have in your wallet the less for "fine" will be if a crooked cop tries shaking you down. Sidenote: "less" does not mean "empty".

All the civilian people I've dealt with have been absolutely wonderful. The only Spanish I know involves ordering beer but that's always been enough. Be happy in your dealings with people and they'll be happy back at you. Try the foods, dance to the music, smile a lot and tip well. Be respectful, don't get drunk, don't boast or brag.

In most respects being in Mexico isn't much different than being in any big US city. Most people are great, some are bad, a few are really bad. Keep your eyes open and stay in the well-lit areas.

Do either of you speak Spanish? That always makes things easier.

Man, now I'm hungery for real Mexican food and some ice cold beers...

-Blast

Uno cerveza por favor...