am considering a trip to Big Bend NP, Guadalupe Mts. and Carlsbad next year. (carlsbad questionable, only because caves are not my thing, but was impressed with the outside of Wind Cave in the dakotas and suspect carlsbad may have some neat features outside the cave). I am trying to figure out the best time of year to go. I would be going for the hiking and birding. i am not a big fan of heat, but if the humidity is low, it's not so bad. It looks like April might be a good time. not too cold at night, not too hot during the day? any advice out there??