Yes, on condition you have your government-issued visas for both countries: having a visa for either Mexico or the United States DOES NOT automatically grant you access to the other country.
does a citizen of Mexico need a passport to go from the us to Mexico and back? He is legal to be in us but not a us citizen.
As long as you have a US visa with you, you can also enter Mexico.
If in Mexico travel north. There is a border crossing. Pass that and you are in the US
Yes, Mexico is a foreign country.
San Diego, California.
8 million
No, but you will need a passport to get back into the US.
I'm assuming you are a US Citizen. It should not be too difficult for your spouse to get a tourist visa if that is what you mean. If your marrying future spouse here in the US I would recommend filing for residency BEFORE leaving for Mexico (6 month to 1 year approval wait), but this is based on staying in US until residency is approved! If marrying in Mexico apply from there or while visiting US (better) so visitations to the US do not become a problem once residency is approved. I would check with US Embassy in Mexico or IRS office here, depending on where you are currently living.
Mexico is one of America's largest neighbours, sharing the second largest border with the US. They are the third largest trading partner of the US after Canada and China.
Mexico is the immediate neighbor to the United States, just south of that country. As Paraguay is a South American country, to visit the United States you would have to pass through or fly over Mexico. Therefore, Paraguay is closer to Mexico than to the US.
No. Nowadays with the Mexican War on Drugs, most cities on the US-Mexico border, including Matamoros, are quite unsafe to visit.
Yes. Recent agreements allow for US visa holders to enter Mexico without additional documentation -- besides the passport, that is.