Really appreciate all the ideas and thoughts! This feels like a once-in-a-lifetime chance to determine where I'm going to live, so thank you for your advice. Given what's been mentioned and internet research, how I feel so far...

Los Angeles: Does it feel like you're in a big city or is it too spread out? My desire to live in one (besides work requirement) comes from loving the busyness/culture in Chicago. Also, seems to be a lot of confusion over how good the public transit is, both here and elsewhere online. For me, there's two real questions (yes/no preferred... don't really need neighborhoods/examples yet):

1. If I live in an area that is nice/trendy with young professionals, will I be able to get to/home from bars late at night on weekends in less than 30 min for less than $15?

2. How centralized are companies? Is there an area I can work in (less than 45 min from a young professional trendy area) where I'll be able to get to most other business meetings in less than 30 min/$15?

Miami: I'm worried that the Jewish community there is older and there aren't many young professionals. Is this valid? Also worried that it may be more of a suburban v. urban city (is this the case?). Seems like the public transit may also be a concern.

San Diego: Seems to be close on all factors, but only really aces the weather test. A bit smaller city than I'd like (I imagine concerts, etc. often skip over it in favor of LA?), seems like public transit is only OK, and the Jewish community is a bit smaller than I'd prefer.

Melbourne/Sydney: Intriguing ideas... Similar to San Diego in that both are smaller cities than I'd like, seems like public transit is only OK, and the Jewish community is smaller than I'd prefer.

DC: Doesn't seem like it is year-round warm weather. What's it like in the winter? I have no concerns about it being too hot (I'll manage).

Tel Aviv: Seems like it may be a bit too small for me. Also the only place where cultural considerations come into play for me. I'm comfortable with Asian cities cause I've been there, but haven't spent time in Israel. Is it easy to get by not knowing the language? How does it compare with major US cities?

Cities not in the running but mentioned by others:
Montreal, NYC, Chicago, Boston, Seattle, London, Baltimore, SF (bad weather)
Singapore, Hong Kong, Dallas, Houston, Austin, Bangkok (small Jewish community)
Denver, Portland, Honolulu (too small)