Tesla will offer up signs if you request them for your destination charging install. Two of the destination charging locations I've helped get put in, the owner specifically didn't want the spots to be EV only. There's three HPWC at each location. The chargers are wide enough apart, and each has 24' cords, so even if the "prime" spots to plug in are taken, you usually can reach the cords over a spot or two to get to where you park.
One location has the chargers kind of at a side lot so Icing isn't a huge issue, the other has the chargers right next to the entrance so they are almost always iced.
Thankfully demand for charging isn't that high so it's not a huge problem yet. I mentioned it to the property owner, he was like "yea, well, they either are available, or they aren't.." He was more of the attitude that he put them in as a free service, so people really shouldn't complain if it's not available. If people were paying to use them he'd make more of an effort to keep them open.
Personally the only chargers I ever rely on are the one in my garage, and superchargers. Any free destination chargers are just a nice bonus when they are available. If I need to rely on a charger on a road trip, I'll make a call in advance to try and be sure I'll be able to use it.