Question: Do I have to speak Spanish to go to Mexico?
You don't have to, but it helps! Many establishments that cater to tourists have staff who speak English, and you'll find that most restaurants in tourist areas have bilingual menus. English is a required subject in Mexican schools, and many people are eager to practice their English with tourists, however most people in Mexico do not speak English.
Mexicans will appreciate any attempts you make to speak their language. Learn a few greetings and simple phrases in Spanish. Buy a good phrase book, such as Berlitz Mexican Spanish Phrase Book & Dictionary (buy direct) and take it with you. Consider it a challenge and an adventure to find ways to communicate!
About's Guide to Spanish Language has a great section on Spanish for Travelers.