You don't need wi-fi to get Munna, silly. XD
After beating the first Gym, just go into the grass right of that city.
Also, in the shaking grass, there is a 5% chance of meeting a Musharna! <3 Munna evolves through the use of a Moon Stone, but now you don't need one for a Musharna! That may be a little harder battle though, so be careful. :3