What region would your journey begin in?
Probably Sinnoh. Much as I love the three regions that preceded it, Sinnoh appeals to me the most; it's just the right mix of countryside and city.
Where in that region would be your hometown?
Solaceon Town. Much as I love colder climates, I've always lived in small villages, and a smaller community like the one in Solaceon Town is one that I'd find comfortable, if not quite as appealing. It's about as close to representing my home as any location in any Pokemon game has ever come.
Assuming you get it from an egg, what Pokemon would become your partner?
I'd quite like a Misdreavus, although I'd be equally happy with a Petilil. Practically speaking, something like an Onix would be better for me, though - something that can carry me over long distances, or is so huge that people would think twice before crossing me.
What nickname would you give him/her?
The urge to call a Misdreavus "Little Miss" would be overpowering...but my Pokemon usually get music-inspired nicknames. If a male, probably Waltz. If a female, either Sonata or Crescendo.