well when I'm at low RPMs, and just cruising, or at a stop light for more than 30 seconds my temp guage will slowly rise, and usually keep going slowly to almost 3/4 the way up. But as soon as I start revving it a little bit while stopped still the temp will start to go back down to normal pretty quickly. Also I live in ohio, and its about 90 degrees out now, and I am running 50/50 coolant. Actually it is probably more like 70% antifreeze and 30% water. what could be wrong?

Sounds like the system isn't all the way full. The rpm's aren't high enough to keep the water pump pumping water. When you step on the gas the water pump spins faster so it pushes the water harder. Try topping off the system. Look for leaks too.

add more water to your mix. that much antifreeze will start eating away at the aluminum head over time.

im pretty sure its full, it hasn't had to take anything from the resivor, but i will try adding some more water to it while the motor is running.