Well, it's LA, for one thing. Too much smog to smell much of anything else unless you're up close, right? My guess is, there aren't any orange trees in the city. :)

However, I do have a lead for you on an orange grove. Supposedly CSU Northridge has on their campus the last remaining orange grove in the San Fernando Valley. And the orangea are free to pick if you like. I guess you can just walk through the grove gate and get them.

The idea, then, would be to get there when the trees are blossoming. Don't know how often that happens, but I would guess spring would be your best bet.

As for heaven, I would imagine it smells better than anything earthly. :) Just a hunch.