The National Oceanic and Atmospheric Administration (NOAA) runs an extremely
useful site dedicated to current and future weather trends. I would begin by studying carefully the predictions for the area you intend to be staying. Weather can be very hard to predict in our state, and the spring is hard to predict even by Colorado standards.
I will say that the Pan would be high on my list. As would be the Taylor, if giant fish and huge crowds sound nice. There are a few good warmwater and two story (warmwater and coldwater fish in one body of water) lakes. I do not know where you are coming from or what your objectives are, but Colorado has a sometimes surprising diversity of species on offer. Blue Mesa is the largest body of water in the state, and has some massive lakers. The population of walleye in CO is fair to good as well. May is not a bad time to target them.