Definitely a 4 ohm single cab. You are still going to encounter stairs and other obstacles where you might need to lift your rig. Therefore 2 cabs for your situation would not be good IMO. I think a single mini 12L (4 ohm) is what you are after.
I would also say that from my experience the LMII (LMIII) is the best lightweight amp for a schroe.
I know this is a schroeder thread, but something else you should seriously consider is the markbass cmd121p combo. Its 29 LBS with cab and amp combined. If you go seperate cab and amp the LMII is going to approach 10LBS once you factor in the cables, amp bag, tuner etc. With the combo you save weight. AND you can always add another 8 ohm cab if you can get assistance. Many TBers have been very impressed with the MB cmd121p. My opinion is that it sounds better (much fuller and warmer) than the schroe mini 12 cabs. I've owned both.
Edit: Just to add that two 8 ohm cabs will sound much fuller and louder than a single 4 ohm cab (assuming they are all the same cab). Also be weary of published weight specs of cabs. They are often wrong.
I would also say that from my experience the LMII (LMIII) is the best lightweight amp for a schroe.
I know this is a schroeder thread, but something else you should seriously consider is the markbass cmd121p combo. Its 29 LBS with cab and amp combined. If you go seperate cab and amp the LMII is going to approach 10LBS once you factor in the cables, amp bag, tuner etc. With the combo you save weight. AND you can always add another 8 ohm cab if you can get assistance. Many TBers have been very impressed with the MB cmd121p. My opinion is that it sounds better (much fuller and warmer) than the schroe mini 12 cabs. I've owned both.
Edit: Just to add that two 8 ohm cabs will sound much fuller and louder than a single 4 ohm cab (assuming they are all the same cab). Also be weary of published weight specs of cabs. They are often wrong.

