Seaairugh

Or into route 213. Have another area blocked off by Pokemon like the Sharpedo's that blocked you off between Johto and Hoenn until you gain access.

There are free options to travel between the first three regions; for those of us who are still poor and are willing to walk, being able to go to Sinnoh for free would be great. I was thinking to add another passageway on route 25 followed by surfing into Pastoria.