At the $100 and $200 games I am able to bluff even when I am not representing a hand. Made up example: I raise with A2 with no hearts and get called once from EP. Flop is . I btp and get called. Turn is and it goes check, check. River is , he checks to me and I bet ½ pot and take it down.

This is a pretty easy read that he has either A2 or hearts so the river bet takes it down the majority of the time. However, for anyone paying attention to the way I play I am also representing A2 so the only way that river hit me was if I had A23. Also anyone who is paying attention will also notice that I like to river bluff.

At the $100 / $200 games I have ran into a couple of players who I won’t make this play against because they will notice that I am not representing a hand with the river bet. As I move up will I run into more and more players that will notice this and I will have to phase this play out of my game? Or will everyone still be basically playing their cards?

in my experience, as you move up, you will both get called more and get played back at more in these situations. furthermore, if someone is going to chase, they will often "chase" by being the aggressor on earlier streets, so often the amount left behind on the river is trivial (if there's any at all), so a bluff won't really work.

like i said, this is a tendency as you move up -- you still have donkeys against whom you can make these plays, they're just less common.

there are MANY ways to bluff at any limit -- you just have to customize your bluffs to your audience.