A KLR250 seems like it would be well suited for what you want it for. Given I may be biased as I just bought one a couple weeks ago. It is also my first bike, I've had no previous experience with motorcycles at all. So far I've been riding it on some nearby dirt trails until I get the proper endorsement on my license. Did take it onto the highway for just a couple miles and got up t0 65mph without a problem. Felt a little 'twitchy' at that speed, but may just be my lack of experience more than the bike's handling. It really is a blast to ride on the trails though, and I'm definitely looking forward to exploring more trails around the Prescott area as I gain riding experience. Have already been looking at different racks for it, it seems to have a much smaller following and aftermarket compared to the KLR650, but does look like you should be able to find most accessories you would want.
I've just started looking into the maintenance aspect, and from all I hear they are pretty durable bikes. The U.S. military chose the KLR250 for some of their SOF teams, so that should mean something about it being reliable and dependable hopefully. Other than simple things like keeping up with cleaning the chain, and fluids and filters, the one recurring remark I've seen has to do with checking the valves. Apparently neglecting to frequently check the valve clearances is one of the most common causes of many problems. Even though my 2005 with 7,000 miles seems in great shape, and has no problems kick-starting, I'm thinking about having the valves checked just as a precaution. Will also think about maybe trying to perform that work myself at some point. But for now anyways I'm just focused on learning to ride well and figuring out what gear I want (helmet, boots, etc.). As far as weight, the manual says 260lbs., so I am looking into whether I could carry it safely on a carrier on the back of my LR Discovery II.
Now to be fair, the Yamaha TW200 and some of their similar dual sport models, do tend to have great reviews also. I know the TW200 is also known for having a shorter seat height that helps shorter riders. Well good luck with whatever route you go, and I'm sure you will really enjoy it. I know I do!
These are some pics of my '05 KLR250 during the last couple weeks since I got it.