Ryhorn is not in any specific place in the Safari Zone. Just check around and search through the grass, and hope to find a Ryhorn. Ryhorn should be pretty easy to find in the first area you enter, though.
In HeartGold/SoulSilver you can find a Ryhorn on Victory Road or in the Safari Zone. In the Safari Zone, it's in 'savannah' areas.
Mach Bike Section of the Safari Zone
you have to evolve a ryhorn from the safari zone
Safari Zone(Encounter Rate is common)
You should be able to get him eventually by roaming around thru the grass.
You can catch one in the Safari Zone and Cerulean Cave.
in safari zone, but you will need a mach bike and maybe some pokeblocks or it will flee very easily.
first u hav 2 capture a ryhorn in the safari zone and then i think it will evolve 2 a rhydon at level 50
its boring only thing u get is doduo,ryhorn,that big word pokemon,chansey,etc. but lucky u can get a dratini
you go to the safari zone bring the arco bike. once your in the safari zone go left until the patch of grass then go up then get on your bike and you will see that a white thing then get on that and you can't go farther press b and up at the same time then go forward and u'll see a patch of grass go in look around in it then eventally you will find ryhorn and phanpy in there(phanpy's are rare!)
I believe a Pokemon Trainer can catch a Rhyhorn in the Safari.
it depends where you go in safari zone. for example when you go into the entrance, you find oddish, etcyou can get pikachu, phanphy, girafarig, pincir, and the big blue Pokemon beginning with a w. :)