new in town? welcome!
the problem with your way into town is that centre ave goes through the hill district, so you'll be climbing up a long unnecessary way.
as for your return trip, forbes ave is one way out of town, so that won't be much use to you heading back.
if i were making the trip, i would do either forbes into town, then jog over and do the 5th ave sidewalk (some others who actually go this way can help you with tips on that), or perhaps, as you said, the jail trail to bates, or even to junction hollow (it's longer, but more enjoyable, in my opinion).
on the way back, fifth ave from oakland to downtown isn't bad at all, and it's my preferred route if i'm heading from the east end to downtown on a schedule. there are a number of good options, though. for example, you could head through junction hollow, across the hot metal bridge, and up the slopes, if you're feeling spunky.