Physical Space

I don't know where to find some physical space at my school to make lesson plans and keep my materials, here is the problem...
The school I am teaching at has an all-male PE department. The school was originally built with one PE office accessed through the male changeroom and one PE office accessed through the female changeroom. These offices were separated by a wall. Recently, a door has been put into this wall so that the two male teachers can access the offices from the male changeroom side. The door to the female side is still there but I always had to enter and exit very carefully to ensure that there was never a line of sight into the female changeroom. In addition, once inside these two offices it is very hard to move. They are jam packed. There is definitely no room for me in there. There is one female staff washroom in the school, adjacent to the staff room.

Where should I get changed?
Where should I keep my materials/other clothes?
Where should I plan my lessons during my spare blocks?

All in my truck since it is parked on school property, where we are supposed to be for the entire instructional day?

It is a little cold for that in the Rockies in the winter.

My best idea is to do it all in the staff room and women's staff washroom, but is it going to give a bad impression if teachers always see me "hanging out" in the staff room? How about the other female teachers getting a bit upset because they can't use the washroom because it takes me the whole 4 minutes we have between classes to get changed?

Any brilliant ideas? What kind of physical space have you obtained at your schools?