When people are considering making the move to Mexico from a foreign country, one of the first questions they ask me is "Do I need to learn the language?" My answer is always the same - a resounding "YES!" While it is possible to live in Mexico and speak only English (especially if you live in an expat hotspot like Los Cabos or San Miguel de Allende), I don't recommend it.
Learning the language increases your ability to connect with a whole new set of people, understand what's going on around you, and gain a deeper understanding of the culture. It is especially important in business - when people see that you are trying to learn their language they tend to be more helpful and appreciative.
If you are interested in learning Spanish, I highly recommend checking out the Rocket Language online course series. They even offer a sample 6 day course for free - so you've got nothing to lose and everything to gain!!!