My ds routinely plays alone outside. We have a fenced in backyard, and neighbours that are older (ds is 3.5, and our neighbours are 4 & 8) so they are in school. Ds will play with them when they are in the yard, but when they are not, he plays by himself. I have a 3 month old dd and cannot be outside with him entertaining him. I also think it's important for him to play on his own, and enjoy being by himself.
Some things we have outside for him:
sandbox with loads of things play with in it
sidewalk chalk to draw on the patio stones
lots of discarded plastic containers for 'collecting things'.
If he's bored, I just give him a task (i.e) go find your favourite rock and we can paint it later; or please pick mommy some beautiful flowers (we have wild flowers).
As far as the pretend play, I don't know what to tell you. I'm not a huge fan of it either, but I'll play into it (i.e) "I'm so hot, could you please go and make me an ice cream cone?" etc.
I hope some of that helps -- I'm sure your doing a great job, your dd doesn't need to be entertained all day...pick and chose the play you want to do with her and encourage her to do the others on her own.