Great suggestions, thanks!
At the moment I don't have a hiking buddy; I plan to do the hike solo, and if a hiking companion materializes, even better. I'm also not experienced enough for Big Sandy Lake, although it sounds awesome. I only have done 3 multi-day hikes, and those were on the easy side.
I hadn't thought of transport to and from the trails! Thanks for pointing that out. I also didn't figure that resupplying might be an issue. Seems like the AT might be a better choice for a beginner than the JMT.
I'll also check if there are any hangouts happening when I know my travel dates. Probably a great place to pick up additional advice.
Please keep the suggestions coming - it helps to hear first hand experiences!