It depends on who gets in and when.
Sometimes on summer nights we just lower it to 96 or 97. If people are coming over duing the day we have lowered it as low as 92.
Just be careful, if you want it lower, set it to be lower a few days in advance (or let it run with the cover off for a long time). Good tubs try not to lose heat, and if your tub is sitting in the sun, it could take a long time to cool down.
That's if you want the "sit in the tub for 3 hours with friends" soak, or you have young-uns in the tub.
If you still want the therapy soak, jumping in at 102 or 104 will not be much worse as you won't be in for more than 10-20 minutes anyway.
I was on a cruise last summer in the carribean and it was *hot* but the hot tubs on deck were up around 101 or 102 and the tub was plenty popular even with the sun beating down.
-Ed