If you go, prepare for a steep ascent with at least one hands-and-knees rock scramble. You won't need specialized equipment, but you will need sustained endurance and lots of water. No trails will take you directly to the tower, so you'll be bushwhacking uphill for some time to get to the cache. As part as the challenge, I'm going to leave the job of determining the best approach up to you. Be sure to consult your favorite topo map carefully and plan your trip before you head out.
Take a look at the mountain and you'll find you can't really walk in a straight line to get to this one. The tower is perched on a high stone edifice that'll take some careful route choices to deal with. Your GPS won't help you find the route to the top; a good map will, so I suggest only using the GPS once you're on top and in the area.
The view from the top is spectacular, take time to enjoy a well-earned rest once you get there. The cache itself is located in a rock crevice southeast of the tower. It's a two-foot length of 3-inch Schedule 40 tubing, so bring small stuff. Please note that to the passing tram passenger the container might look like an explosive device; you might want to keep it hidden while the trams pass so as to avoid any suspicion that you are about to commit an act of terror on the tower. (Thanks to Southwick and Zygodactyl for noting this.) I posted some photos in a note log on June 11, you might want to print those off to use if you get stuck and can't find it- It would really stink to come back empty handed!
A few reminders of how to prepare: This is a longish off-trail hike, so start early and bring raingear, sunscreen, and LOTS of water. You really don't want to wear shorts for this. My trip to the top took almost all day (round trip) and was very strenuous. Mind the cacti, snakes, pointy plants and too much sun exposure. Most importantly, trust in your intuition and be safe.
If you have any questions, email me and I'll be happy to give hints or clarifications. I hope you enjoy the challenge, and good luck!