Do I have to learn Spanish?
When we announced our move from Dallas, TX to Isabela, PR this is one of the top questions I was asked. The answer is, sort of.
All road signs in PR are in Spanish, so you do need to learn some basics. Standard road sign shapes and colors apply; you'll know pare means stop. However, your GPS will tell you to head west, and the sign on the road will say oeste. Other signs, such as no right turn on red, will be completely foreign to you.
When ordering food, you have a 50/50 chance of your server speaking English, and a 50/50 chance of your menu being in English. The good news is that someone working is an English speaker, and your server will track them down if necessary. This is true for drive thrus, too.
Fortunately I was fluent in Spanish in high school. While I can't speak as well I used to, I can still read Spanish pretty well. Being immersed is bringing back the language quickly for me. I should also mention Google translate really comes in handy in situations where an English speaker isn't available.
Can you survive in Puerto Rico without speaking Spanish? Of course. But I wouldn't want to. Ask anyone who knows me - I love to talk! I've been here for a few weeks and I've already missed out on making new friends because I wasn't comfortable with my Spanish speaking skills. Give me a few weeks with Rosetta Stone and I'll be hablando up a storm. :)