Mount Myoboku: a different space/dimension? There are two ways to enter mount Myōboku:


A secret path from Konohagakure
Reverse summoning


So there is no way (as known so far) that you are traveling somewhere and by mistake end up landing on mount Myōboku. Neither is it shown on any map in any episode.

I assumed that it's a different space or world. (Than the shinobi's)
As stated in the wiki:


  For a human to get to Mount Myōboku, it either takes a month long travel on secret paths from Konohagakure or, if they have a summoning contract, they can let a toad use the Reverse Summoning Technique. According to Fukasaku, Mount Myōboku is impossible to find by foot for those who don't know the secret route. (Chapter 409)


But whether or not it is in another dimension is nowhere stated. Additionally it is not shown on the World map of Naruto. So it could be on an unknown place on this world (as on an island not yet discovered by the shin-obis or as you said in another dimension or even on another planet.