I actually built and ran a pirate radio station in Tucson 15-20 years ago, Radio Limbo 103.3. I agree with your tip, but I took it a step further. The transmitter was a 1 watt unit that we hiked way up into the mountains north of town, giving it a 3000 foot elevation advantage. We transmitted through a Yagi made from a modified FM receiving antenna. The uplink was on UHF, and the rig was solar powered. It covered most of the city (about a 10 mile radius in the preferred direction) reasonably well.
The other thing we did, which really made the station great, was to get about a hundred DJs to volunteer for 1 or 2 hour slots, to make the programming interesting.