The whole point of dating is to get to know the person you're dating.
Going out on a date, or two, or three with a person isn't a lifelong commitment.
As long as you and your date are both aware of that, what's the problem? Of course once sex or other things come into the picture, you change it up a bit, but the fact remains, you meet someone, if you think they're worth going out with I say, why not?
You're still a little hung up on your ex, it happens. If you know someone, and you want to go out with this someone, then go for it, maybe you'll have a bad time, due to your issues, and then you can politely excuse yourself. Maybe you'll have a good time, and it'll turn out this is what you need....you won't know till you try, but as long os you're honest with your date, I don't see why not.
As for your ex (Someone stated concern for what your ex will think), well they're ex for a reason, so you're bettr to put your feelings ahead of theirs.