I'm assuming you're purchasing a shortboard since longboards tend to be longer that 9' in length (in Hawai`i, anyway). They can range anywhere between 8'-10'. I wouldn't suggest learning on a shortboard because they tend to be thinner and skinny...hard to balance on, difficult to paddle, and maneuver, etc. I'm no expert myself, and I really don't think I've reached advanced status at all -- and even now it takes me a while to get used to it especially if I haven't been out in the water in a while.
I still maintain that longboards are the easiest to learn on, but that's just me.
As far as height goes, I rarely base my board length on height because I pay more attention to the weight as well as the width of the board and how buoyant my board will be.
Try and call around the different surfshops and get their opinions. My nephew's about 80 lbs and his 5' shortboard suits him well. I'm 120 lbs and mine's 6'2", 18 inches wide and about 2 inches thick.
If you're going to buy a board, I'd suggest getting a decent used one, especially if you're just going to be learning for a while. Those in good condition will cost at least $100. You really don't want to learn on a new and classy board...those will run you anywhere between $350-$500. I know a lot of shops also buy back used boards (not at the price you paid for, of course), so at least you'll get something back.
You might also want to look at funboards -- not as long as longboards and somewhat similar to shortboards. I hear they're great to learn on. Unfortunately I don't know much about them.
But I'm sure the local shops will be more than happy to assist!
Again, I'm no expert, but the above things are what I usually consider when I'm out shopping with friends for new gear.
Good luck and have fun!
Threaded Mode