Lost on the JMT, impossible!!! yes, the signage coming into Red's ain't that great. I think it's all a ploy by the folks at Red's to make the burgers taste (even) better once you thankfully get there.
I always do my best to get into Reds, eat, make calls, get a shower and then get out of there, as I don't much care for the "backpackers camp" . . . or rather, I should say, I love spending the night on the cones, so much more.
There are two trails headed south from Red's . . . one is the current "official" trail and the other is--to the best of my knowledge--the old JMT. . . the official trail, as noted on the Harrison map(s) picks up down around the stables and wanders up into the burnt forest, taking you BETWEEN the two RED CONES, where you then cross the creek (below Crater Meadow) heading south on the JMT.
If you get to the creek and don't cross, but just head left, or east, you'll end up going backward towards the Mammoth Junction (or pass?) trail . . . and possibly find yourself back at Red's if you're really not paying attention.
also, on the official trail, if you are not paying attention, you won't even realize you're moving between the cones.
The other trail headed out of Red's is just behind the restaurant and takes you up, junctions with the mammoth pass trail and then, after plodding along in the dead forest, drops you into the dark woods and then, skirts the backside of the major cone----and here, you can walk out and up to the top and even spend the night.
In the morning you drop back down to the trail and meander into Crater Meadow and the creek crossing.
If you do spend the night on top of the cone, PLEASE try and leave it as it is. Don't try to build any fires----or bury anything ( like TP) . . . it's bad enough that there's horse poop up there.