I suppose you could leave them in the car, but you will do a heck of a lot of walking to get a uniform for each game.
When I was there last year I was getting wifi coverage in the bunkhouse 33B. That had not been the case the year prior though.
You can normally work as many games as you want. I averaged 3 a day for the first 4 days last year. The fields will schedule a 2 man crew but you can go 3 and 4 man to work on new skills.
It gets cold. Granted I have always been up there in week 1, but my first time it was 93 when I left Georgia and 53 when I got there. Add some rain to that and you will want a jacket. Black jackets seem to be in short supply up there.
I've been there three times and I have seen 18 year olds and a 93 year old. There is a wide assortment so I have no clue what to tell you about the average.