Tim, if you can afford it, get an aluminum channel trailer, not a galvenized. Galvenized is a hot dip over a steal trailer and is still vulnerable to rust at certain points on the trailer. trailers get dinged up, it doesn't take much. Once scratches or dings occur, your trailer is now vulnerable to corrosion/rust.
I had a galvenized trailer in Hawaii and it still had rust spots on it and it was only 2-3 years old at the time.
As far as running the boat in saltwater. I ran my Malibu Sportster LX and Wakesetter VLX in saltwater and was VERY anal about certain things. Don't let one session of riding go by where you ignore soaping everything down, salt away flush, wash trailer down anytime it touches the salt water, etc..... That one time ignored, is where it all starts going wrong.
I used about a half can of wd-40 on the engine and trailer after every time I took it out on the water. Sometimes that was 3-4 times per week. Who cares if your engine gets all gunked up with WD-40, atleast you have a layer of protection over it. After I moved to Arizona with my Wakesetter, I realized that I was so anal and now recognize that my boat looks better than some of these other boats around here that have been in fresh water.