Have you tried talking to the guys you are referring to? Tell them you are interested in something serious if that is what you want with them.

I think as a general rule guys always try for sex even if they don't want something serious or commitment. I think you have to weed people out that are just looking for that and bot for what you want. Talking and being straight forward is the best way in my opinion. At least they know where you stand and what your looking for.