If you want an interesting, contrasting, and facilitating subject (and I'm being slightly biased here), French is a great way to go. If you're enjoying it now, it should get better at AS and it definitely gets more interesting at A2.
Otherwise, I would say to not let your opinions of teachers at GCSE influence your A-Level decisions, but if you're not enjoying it as much as you enjoy other subjects, chances are that will continue - don't take a subject just because it looks good, you'll probably do better if you go for something you enjoy, especially if you can explain your choices.