I think the most important thing is to speak to the neighbouring plot holder that shares the same light/slope/ trees alongside aspect, and presumably similar soil- they would know more about the drainage and any problems.
Where are you based urbanarcher? Did it get a lot of rain and snowfall? If so, don't judge the wetness of the ground to harshly until you've spoken to them. There's plotholders near me who's plots are completely waterlogged now but was fine in the summer- they had an enviable harvest- they're at the top of the hill and I'm at the bottom (mine is completely fine!! No puddles- i wouldnt have expected that! They may need to stick a drainage gap around their plot?)
I guess... think of what is the MOST important thing on a plot to you, and what are the deal breakers that would make you wait another year? (My deal breaker was.. if i was offered a tiny plot.. and even still i'd have struggled to turn it down)
I think every plot that comes available has its down side in some way- whether its because its ridiculously overgrown or the soil is heavy, or because of distance to the hosepipe (which is a chore i would find harder to deal with than most issues) - everyone usually has something to overcome- (As long as you've no horsetail- that is a nightmare and a half)
I'm guessing it will be mostly in sun from sun up at 6am through to about mid afternoon if the map is anything to go by, which isnt bad! (more than my garden gets, and I've grown toms in it!!- and you can put your real sun-lovers like tomatoes away from the trees?
Usually if theres more than one plot available you get a choice, don't you? (or at least i did)
On a really positive note.... lots and LOTS of leaf mold in the composter!!!