Expect huge crowds.
As for what you should/shouldn't ride...
In any other park, I really wouldn't ride anything except maybe Twister II. But you'll get really bored if that's all you do. So ride all the coasters just to say that you did (wait, you'll still be bored...). Mind Eraser will have the longest lines by far. Twister II and Boomerang are 2nd, and Sidewinder fluctuates a whole lot. Sometimes Sidewinder's a walk-on, and for some reason 15 minutes later the line is full. Weird.
There's 2 reviews of SFEG at
http://www.coasterforum.com/boards/s...&threadid=7587 along with 2 reviews of Lakeside Amusement Park, also in Denver and home to the ACE Coaster Classic certified Lakeside Cyclone, built in 1940.
Hope you have a good trip!