What are the best neighborhoods in Los Angeles for 20-30 year olds?

If you want to live near the beach, Redondo Beach is the most affordable of the beach cities Manhattan, Hermosa and Redondo. You can rent a condo one block from the Redondo Pier for about $1300-1500 a month for a one bedroom. Redondo Beach is a laid back, beachy kind of place with plenty of restaurants and bars. On weekends, you can ride your bike to Hermosa's Pier Avenue and hang out with all the other 20-30 year olds or you can surf right outside your door. If you're a walker, you can keep pace with the dolphins that swim near the shore between the pier and R.A.T. beach (Right After Torrance) as you take the 2 mile beach path or walk on the Esplanade.

West Hollywood, Los Feliz, Glendale City Center, Manhattan Beach, Santa Monica

I would say Manhattan Beach, Santa Monica, Los Feliz, and West Hollywood.

I like to cut to the chase. Venice, West Hollywood, Los Feliz, Toluca Lake and Culver City. Many more, but they are secret gems.

The beach cities, without a doubt, are a great place for young professionals. Hermosa & Manhattan are huge volleyball meccas and have a great beach life. At night, the Hermosa Pier which is lined with bars and restaurants is jam packed with locals. People all over LA come down to Hermosa on the weekends to go out. I'll warn you that the lines are endless unless you have a connection at the door. (But it's like that whereever you go, right?) The key is to hang out at these bars during the day when it's less crazy and make friends with the bouncers so when you come back in the evening they know you. Keep in mind that these are small beach towns. If you're looking for something larger with more art/culture, then Santa Monica is great. You have the 3rd Street Promenade and all the shops and restaurants on Montana. Santa Monica is a much larger city.There is a huge contingency of young profesionals. Venice also is a more off-beat area and great for young people. It's artsy and has a lot going on too. I love the shopping, bars and restaurants on Abbott Kinney and Main Street. Abbott Kinney also has an awesome street fair the first Friday of every month which is fantastic.

West Hollywood, Venice, Santa Monica, Los Feliz, Silverlake, Some parts of Hollywood, and the Marina. Manhattan Beach is great but it's kind of far so it depends on if you have a commute for that one.