Well, I did French at school and was OK at it (o level) but have forgotten it all since. In my experience a little bit of French is just about enough to invite derision from the locals when you go there.
Like Yellow Fang above, I also found German to be much more appealing – for one thing the pronunciation is largely consistent and clear, and although the grammar is complex, it does sort of make sense (apart from the randomness of whether something is masculine feminine or neuter). I found that the biggest problem with German (quite the opposite of French) was that as soon as they twig that you're English, they're only too keen to show off their English so actually getting practice can be hard.
I am about to have another go at learning Spanish – my other half is Spanish and I've been meaning to get to grips with it for ages. I shall shortly be signing up with the local college for Spanish lessons (again). I've heard that it is supposed to be a lot easier to learn than French or German, and having got relatively fluent in German I thought it would be a doddle but I suppose I just forgot quite how long it took for my German to get where it is now.
A big factor in what language to learn is whether it appeals to you, and whether you're likely to go there regularly. I loved the 'logical' nature of German and the amusing sound of the words, and then found that skiing trips helped me practice. Eventually I got a job there for a year and now have many friends there, visit regularly, am on German bike forums and even make a little money on the side doing translations into English for a German hifi manufacturer. My French is all but forgotten. So, try to pick a language that you think you like the idea of, and where you have someone who you can practice on, or if it's somewhere you're likely to go on holiday. That way, you're more likely to do better, and it could really open up unexpected doors for you like it did for me.