This is actually a really good question. I was thinking about something like this once before. I think I was walking home from school, wishing that I could morph into a hawk and fly home, when I started thinking--even if I could morph, where would I do it?
By my old high school, there's this patch of woods, or a forest, or whatever, but it's not what you'd call dense or thick. In the winter, you'd have no coverage, and even in the spring/summer you'd risk being seen by someone--though, most of the people known to hang around that particular patch of woods were consistently high, so maybe it wouldn't have been too big a deal...
I think it's worse, considering how far we've come in terms of servelliance cameras and stuff. I mean, it only takes one kid walking around with his iphone to blow the invasion for you. What if that kid saw you morphing? I'm reading book 18, and the part where Ax and Visser Three have that air battle--seagull versus Kafit bird-- just made me think, "They'd never be able to cover that in 2011". People have camera phones, and iphones and whatever. That battle would have been on youtube in twenty minutes--but that's only because my computer isn't especially fast (not that I'm complaining; I love my laptop!)
I really have no clue where I woud morph. I don't exactly live in a small town. People are always going to be walking by. Most of my morphing would have to take place at night. Or I'd have to bus to a secluded area.