First off, I would not run to Mexico. If for some reason you want to get back, you will be screwed.
Crime against Americans in Mexico is higher than you would imagine. You could end up in a Mexican jail, and they won’t take care of you like in America… so if you go, remember that you are subject to Mexican law. If you think that you can just get back into the US, you are seriously mistaken. As of Jan 1, you are required to have a US passport to enter back into the US. You may even need one to exit the US, though I don’t know for sure as it has been a year before my last border crossing into Palomas, MX.
Then the question of work… you know for a fact, (as you are in CO) that illegal immigration is high. What is the reason you may ask? Mexico doesn’t have a great job market. How do you and your eighteen year old boyfriend plan to make a living?
Lastly, it is still illegal no matter what, for you to run away. Unless you are emancipated legally, you are still required to obide by your parent’s rules. Your boyfriend can be charged with kidnapping, as he is an adult, and you are a minor. Mexico has a law that cooperates with American law, and they will extradite you if the Mexican citizens don’t hold you agaisnt your will and demand your parents pay ransom.
The important question is why do you feel you need to run away. If it is home problems in which your life is not in danger, or you are not being abused, why not try to work it out.
If you are being abused and or threatened, seek counsel or contact the police.