Solving the immigration issue

During the past year there has been a great deal of debate on what to do about illegal immigration to this country primarily from Mexico.
Proposals have ranged from "Round 'em up and throw them out" to "make 'em pay $5000 to become citizens(yeah a lot of illegal immigrants making minimum wage will be able to plunk down that kind of cash). None of the proposals can make everyone happy. With this in mind I have come up with a new plan that should satisfy all americans.
Fact - nearly all local and state governments as well as our federal government have spent vast sums of money making the United States nearly bilingual. Everyone calling a large company or government agency has heard this "Para Espanol press numero dos". And Spanish is a very easy language to learn.
Fact - more than 13% of our population is Mexican
Solution - Make Mexico part of the United States. Think of all the land and resources that could be developed with US money from both business and the government.
Think of the billions of dollars saved by not having to guard borders. Now our borders would extend to central america. The rest of our borders would be water. It would certainly be easier to patrol the tiny border with central america than the entire southwest USA.
I think most mexicans would welcome the opportunity to become part of the USA.
What do you think?