How difficult is it to learn to speak Spanish?

The only language I currently know is English and I’m thinking about trying to learn to speak Spanish for many reasons.

At the current time i’ve no interest in learning to read or write it, just speak. I’d like to learn enough to be able to hold decent conversation and be able to socialise with people.

I like to think of myself as being quite intelligent and generally pick things up pretty easily if it makes any difference.