Renting a car in LA is not necessary unless you plan on a road trip before or after your stay in LA, and overnight valet parking at hotels can be expensive. Uber and Lyft are the most efficient ways of getting around. There are always an abundance of cars available and prices are comparatively cheap to other major cities like New York!
The wedding venue is located in West Hollywood. There are a ton of hotels at all price ranges available in the West Hollywood and adjacent Beverly Hills Area. If you prefer to stay by the beach, Santa Monica and Venice are most popular and are about 25 minutes from West Hollywood.
It can be! But traffic can generally be avoided if you aren't going long distances during rush hour.