IMO ...
There is no rule forcing the players to seek out the Tomb of Horrors.
Acererak didn't exactly make it an easy place to find! The locations given for the individual campaign worlds, are extremely remote.
If characters INSIST on divining the location of the Tomb, and they INSIST on going to it's location, and they insist on uncovering it (even at point blank range, it's not easy to discover), and they insist on going in ... well, they made their own cake, didn't they?
And even then, it's possible to go back. At the beginning of the Tomb, there are things that clearly show the terrible lethality of the place, which at least some of the party can hope to survive. Perhaps they will take warning from these initial encounters, and leave?
If not, then they must eat their cake.
Note: Krynnish kender are an exception to this rule. They will ALWAYS insist on finding the Tomb of Horrors and exploring it. Talking about it's lethality will only make them more determined. For their own good, kender seeking the Tomb should be imprisoned in a Cube of Force. (Anything less than that, and they'll escape.)
How do you 'cheat' the Tomb?
I've changed my mind. I'm not going into that. Let everyone find their own way here.
I'll just say this: go ethereal in the Tomb, and you just might find Acererak HIMSELF (in his FULL power, with a fully corporeal body and all his spells and everything else!) facing you, and then you have a REAL problem. I should know. (chuckles darkly)