If you are doing time in So Cal you ain't gettin nothing but peanut butter all fucken day long, a pair of shitty and dry chocolate chip or oatmeal cookies with a couple of slices of whole wheat toast and a fruit (apple or banana). You'll get two of these types of meal and let's not forget the "purple" or "orange" juice (no actual juice content). You might get a meal with mystery meat that looks like Bologna with a package of mustard and another of salad dressing instead of peanut butter. Breakfast will be a hard boiled egg with a small portion of cereal, milk and some peanut butter with wheat bread. Dinner varies and it's you're only hot meal of the day. Some kind of meat and carb type thing (rice, tortillas, or spuds), and a little salad with a juice. You'll have less than a couple of minutes to eat that shit, depending on if you have to go to the mess hall to eat or if you are allowed to eat in your dorm/cell.
Forget about weights. There haven't been weights in jail and prison since '97 if I remember correctly. If you're a South sider (Latin gang member) then you'll have to do burpees everyday (113 to be exact) in a pseudo-military fashion with th rest of the inmates in your block. This is if you're somewhere where the guards allow you to do exercise. If not (Wayside for example) then you'll have to do burpees clandestinely with the aid of another inmate or else you'll catch some serious shit. Paisas (non-gang Latinos), Woods (white guys), and Brothers have there own system which is usually sit ups and push-ups. I don't remember seeing the Woods and Paisas doing burpees. Brothers are in there own area for obvious reasons so I never saw what they did to keep in shape. There are also make shift weights in the shower made out of tee-shirts, plastic bags, and water that weight about 50ish pounds. You can do curls with those things but if you have any size those things aint shit. Most of the guys in jail are skinny as fuck so those little things effect them but if you have any size, you'll be doing made reps to get a pump.
Good luck man and listen to no one's instructions but the guards and your racial rep. Break that rule and you're getting taken to the back. Once you're settled in you can get aquianted with the store system but that shit ain't all that either and it aint gonna be for at least a week while you are getting settled into your final housing situation. The store is pretty much just chips, powdered coffee and cholocate drink, a shit load of Top Ramen soups, some shit that looks like smoked sausage and othre little things like hot sauce, pencils, paper, advil, reading glasses and shit like that.
Please Scroll Down to See Forums Below 
