Although I can't claim to speak Spanish, I do know enough to sometimes get the gist of a conversation. A few years ago I overheard a conversation that was so clear it was almost as plain as English. When asked what dialect they were speaking, the people said it was the Mexico City dialect. They said it is the clearest version of American Spanish. The point is that just 'Mexican' may not be specific enough. And watch out for that double r.

Note: Spanish speakers tell we that the real differences are in the idioms and usage, more that pronounciation or grammar.