If you have access to the upsers.com website you can see what is in each district. Los Angeles appears to be in 3 districts. It doesn't give figures just for LA unfortunately, The west LA district is probably as close as you are going to get for what you are looking for. Here is what I got from the site.
West Los Angeles District:
Service Area: North to San Luis Obispo, south to Gardena, east to Los Angeles, west to the Pacific Ocean, north to the high desert past Bishop. Six counties (San Luis Obispo, Santa Barbara, L.A., Ventura, Inyo, and Kern) with a combined population of 12 million.
Delivery Fleet: 1,600 package cars, vans, and tractors
Gateways: LAX International Airport and Burbank Airport
10 Operating Locations
South California District:
Service Area: Los Angeles, Orange, Otay Mesa, and San Diego counties, with a combined population of 15.6 million.
Delivery Fleet: 2,284 package cars, vans, and tractors
Gateways: John Wayne, Long Beach, and San Diego
11 Operating Locations
Southeast California District:
Service Area: Los Angeles, Riverside, San Bernardino, La Paz (Arizona), and Hawaii
Delivery Fleet: 1382 package cars, vans, and tractors (149 CNG package cars, 3 LNG package cars, and 11 LNG tractors)
18 Operating Locations (including 5 in Hawaii)