There's an old joke in language teaching circles that goes:

What do you call someone who can speak three languages?
Trilingual.

What do you call someone who can speak two languages?
Bilingual

What do you call someone who can only speak one language?
English!

If the last person sounds like you and you want to do something about the situation, there are a huge number of language schools in the English-speaking world that offer courses at all levels. For instance, a beginners Spanish course in Chicago or Spanish course in London is something that can be arranged at your leisure and can be taken in an intensive, week-long block or as a series of evening classes. When learning Spanish, you will learn different variations depending on the language of your teacher. In Chicago, for example, you are more likely to have a Latin American teacher than one of Spain itself. Pronunciation varies greatly in different parts of the Spanish speaking world. This would be less relevant when taking a German course in Chicago or Italian course in Chicago because pronunciation is much less varied in German and Italian, due to the smaller spread of their native speakers.

The most popular (and, arguably, easiest) languages for English speakers to pick up are the other European languages, which share an alphabet and a number of words. The Romance languages (Italian, French, Spanish and Portuguese) are particularly popular among learners studying a language for pleasure as opposed to for business. The typical mix of people you could meet while taking a Portuguese course in London or French course in Chicago may include housewives looking for something stimulating to do, students preparing for a year abroad and gap year students getting ready to travel the world.

Learning a new language can be extremely rewarding. When you have your first real conversation with someone in a language that is not your own, the satisfaction is immense. It is worth bearing in mind, though, that classes are no substitute for real experience and the best way to learn a new language is always to be immersed in it. For example, taking a Spanish course in London will teach you all about the tenses you may encounter, correct application of Spanish grammar and how to ask for directions, etc, but the chances of you understanding a real Spanish person are minimal without practice.