We've always had to do "alternative" hills down here in vertically challenged RGV to train for some of the more hilly courses in the Cen-Tex area. The other alternative is to run in some of the awesome state parks in the SA / Austin area, but it can get expensive to travel up there.
So we've had to come up w/ some "unconventional" workouts:
Bleachers - Who doesn't love bleachers? Besides, who hasn't done 'em before? The only issue we have with bleachers is that there are only a few high school stadiums that have high bleachers, and all of them are not open to the public (something about the school/coaches being afraid of the public destroying their new & expensive state of the art turf.
Highway Overpasses/Ramps - The good ol' paved hills. As you can imagine, back & forth/over & down repeatedly does get boring. We recently started using an exit ramp that has been closed ~ to change it up a bit.
Construction Mounds of Dirt - Yes, you read that correct. Here, locally, there's a huge mountain of dirt that I think is for sale or construction crews get dirt from.
I guess if I really think about it, we do have "hills" in the valley...of the aluminum, concrete & dirt kind.