Sorry, I caught this thread late. Since I spend half my life reading and getting work done in cafes, and since I have this *hunger* to find the perfect cafe, I've visited about, oh, I don't know, 80 or 90? My favorites:
Java Man, as somebody else mentioned. Breezy, sunny, quiet space in Hermosa Beach. Possibly the pleasantast, openest coffeeshop. Always quiet, always happy. Coffee: pretty decent. Baked goods: OK. Seating: good, hard chairs, and some couches, and nice wooden tables. If I lived nearer, I would go there all the time.
Cow's End, in Venice, on Washington at the beach. Used to be better, than the owner tried to hippify the top floor and put in hard chairs and silver paint in the back room. Anyway, open sea breezes, normally it's very quiet, and I get a lot of work done here. Coffee: pretty good! Service: very friendly, very slow as a consequence of being *very* mellow. Decent smoothies, decent madeleines, and all Boar's Head meats for sandwiches.
I dislike Novel Cafe for being crowded, kind of uncomfortable, and full of the stench of screenwriter-desperation. The place feels squashed. Pretty good coffee, though.
(Note: Gourmet Coffee Warehouse in Venice makes the best damn drip coffee in town, and fresh roasts daily. Good Ethiopian Yergacheffe for $7 a pound! Little seating, though.)
Literati Cafe - weird harsh walls make it echoey-loud and hard to concentrate. Good coffee.
There's a little tiki-cafe near Juquila which is my least favorite cafe in California.
Borders Westwood cafe, normally feels a little stale in the inside, but, when the light isn't too harsh, the patio is frequently deserted.
Rooms Cafe, next to Ambala Dhaba: Japanese art-school/cafe. Very pleasant, comfortable seating, good coffee, Pocky available by the bag. A favorite. Sometimes the music is too loud to work.
Urth Caffe has exceptionally good coffee, but I defy anybody to get a coherent thought there.
Although, nearby, there is Elixer Tonic and Tea, which has a faux-Buddhist zen garden with a strange fake fountain that is just... a stone well, with a rusty pipe sticking vertical up in the middle. There's nice bamboo and rustling wind, but sometimes they pump in pounding indie rock. Weird. But sometimes it's the pleasantest place to sit and do work. Their high-energy drinks, which are basically mixtures of every stimulant known to every culture on the face of the planet (caffeine AND mate AND sweet vine tea AND...), has been responsible for more pages of anything I've written...
Insomniac Cafe: a lot of writers I know seem to like this place, but it's always stuffy, the couches are large and imposing, and sticky, and the place is constantly filled with at least 12 screenwriters looking like they need an IDEA so hard that they're willing to sacrifice their first, second, and third-born child. It stinks of anxiety and forced creativity. Coffee's getting worse, too.
Daily Grind: across the street from Fairfax High School, on Melrose. Notable for having at least two sets of comfortable couches, and, being the least hip cafe in Los Angeles, frequently deserted. Lives on trade from high schoolers escaping for lunch or hanging around right after school. Avoid those two hours and you have the place to yourself. Nice, when they're not blasting EZ listening. Coffee: alright. Snacks: pathetic (all purchased from the nearby bulk goods store... Sav-Whatever.)
Espresso Mi Cultura: three blocks from my house, and one of my favorite places on earth. They've just closed down their gift store and added seats, which makes it easier to find a seat. A nice buzz, about the right level of background music, friendly people, large windows with lots of light, and good, good coffee. One guy there really knows how to make an Americano. Also very good Mexican hot chocolate. Snacks are kind of sad. They also stock Elixer Tonics and Teas, but tend to make them kind of strong... buzz in my heart and I'm too shakey to write strong. I spend half my life here. (Sounds like a few other Chowhounders do too.) I once was here till late in the night, when they had an Anarchist Support Group. Anarchists emotionally commiserating on how everybody thought they were violent. Very charming.
As a bonus, it's across the street from Rodded, the best Thai duck noodle soup in town.
Casbah Cafe: another favorite. In Silverlake. Small Mediterranean cafe/gift shop. Quiet, good to work in, and has the best cafe snacks in town, including genuinely great Turkish candied dates, and sometimes, most specially, they get bread from that nun-run bakery. My favorite pumpkin bread. Also very good Earl Grey. Slightly expensive, though, and the chairs are a little uncomfortable.
Psychobabble: I'm there more than I should be, probably because of proximity to some friends. Frequently loud, frequently crowded, watery coffee, and the worst cookies in any cafe in town, save perhaps the Daily Grind. No, worse. Psuedo-gourmet cookies that fail are far worse than the Daily Grind's standard supermarket cookies.
There's a nice place in South Pasadena, too, I can't remember the name... a block south of the main drag... by a... public library? Nice outdoor seating, very good coffee... they even have desk lamps on all the tables.