Sure, you don't NEED to know Spanish to travel in Latin America. Charades and a few words will get you by. Like a drunk tourist told me on the beach, "you don't need grammar. They get it. Dos cervezas. Two." His wife countered that learned grammar had to do with self-respect - you feel better about yourself when you can communicate effectively. For me, though, learning Spanish was a matter of respect for the countries and people I visited. If I hoped to step into someone else's world and be welcomed, I should make an effort to be able to speak their language. Ethics and responsibility aside, you will have a richer and more fulfilling trip if you can speak some Spanish. It will also be infinitely easier to decode menus, find your bus, and find your way around Xela's steep and almost-on-a-grid streets.
Xela is quickly turning into one of the most popular places in Guatemala to study Spanish. (Antigua and San Pedro are also popular but more "gringofied.")
There are so many choices that trying to choose a school can be overwhelming. If you visit schools, they will show you around and all tell you much the same thing. Private or small group instruction, activities included, volunteer placements, free coffee, homestays... Ask around town and see where travelers are happiest, or check out the options below.
Eureka: Eureka is a popular and affordable school run by a couple of young goofballs. All instruction is one-on-one, and if your teacher isn't right for you, you can switch, even mid-lesson. Afternoons and weekends offer time for activities like movies, salsa dancing, and excursions to hot springs or other attractions. Every Friday the whole school gathers at a local home for a dinner party. Eureka also offers free coffee, tea, cookies, and water, and five hours of free internet. Start any day, $100 USD (including homestay) for four hours per day. Located on 12 Ave - walk uphill from the park and it will be on your right half a block before Calle 3a.
Proyecto Linguistico: This politically-minded school gets rave reviews. Private instruction laced with progressive politics is available for about 130 USD per week, including homestay. They also run a school on an organic coffee finca in the mountains, where students live together in a house and share meals with local families. This will cost you 180 USD per week, but everyone who does it loves it. It's often full, so plan ahead. 5a Calle 2-42.