In many cases, East Pacific storms develop from tropical waves that first track through the Caribbean.
Wouldn't that be, in almost all cases?
They have storms that form from low pressure areas, probably more frequently then the Atlantic (although i'm not an expert on that basin). I'm pretty sure Hurricane Bud from last year formed from a low pressure area that developed over Central America and moved into the Pacific. Hurricane Fabio as well, if i'm not mistaken, had similar origins.