I would avoid both cable and DSL for this size of office, except as backup in case of an outage. Neither of them scales well, and neither of them consistently provides solid bandwidth about the minimums. The 6MB service will peak at 6MB but will not reliably stay at 6MB, particularly when consistently used.
1- I have had good success with Covad Wireless (point to point, not satellite) in the central and east LA areas. It is relatively inexpensive and can be deployed in a matter of days. You should be in a good location for this service. The antenna is similar to a DirecTV/Dish satellite, and can mount without permanent damage to the structure.
--> I used this service for 6 years at a couple of locations in the Commerce area and never had a weather issue. Even when it rains it isn't hard enough to matter.
2- For wired connections, the biggest factor in quality is your local telco and distance to the "central office", which varies depending on the location. I believe AT&T (was PacBell and SBC) is the local provider in your area .. I strongly advise against getting a T1 from AT&T.
3- I have had good luck with Sprint as the internet provider for a wired dual-T1 speed circuit. The back office support is typical of a phone company, but the sales, implementation and tech support were good and the network is rock-solid. A phone guy I have worked with for a long time speaks well of TelePacific and PaeTec. Contact me off line if you want contact info.
Are you planning on running phone service over the same link? If so, there are excellent bundles available which combine VoIP access to the telephony network with internet access and long distance minutes. I believe that TelePacific and PaeTec both offer these kinds of bundles.