The Purple Line to be precise. Metro has come up with several schemes on how it should be done; the one at the right is the one that I favor. It would combine an extension West from Wilshire/Western along Wilshire with stops at LaBrea, Fairfax, La Cienega and Beverly. There's some debate about the next two stops- they can't decide whether they should stop at Santa Monica/Avenue of the Stars of closer to the mall. Personally I always vote mall. The next question is Westwood/Wilshire of closer to UCLA, That's a no-brainer to me; I'll never quite understand the decision to can the #21 bus, which went to campus and was wildly popular with students. This is a perfect chance to make up for that mistake and get a lot of kids to school without a car. It's also a way to avoid taking some very pricey private property for a subway entrance and getting putative pedestrians out of a very dangerous intersection. Not to mention it's a way to keep the Metro people using the Purple line to kill off bus service on Wilshire. Because you know they're thinking of it...
The other stops would be along Wilshire, at Bundy, 26th, 16th and 4th in Santa Monica. But perhaps the most exciting part of this is the "pink line", which would start at Holywood/Highland along Santa Monica Boulevard with stops at La Brea and Fairfax, either La Cienega or San Vicente (uh, hello? Metro? You have property at Larrabee one block away from San Vicente that will allow you a subway entrance with very little Eminent Domaine nastiness), a "Beverly Center area" stop (which the Bev Center should help pay for and offer up the old, unused Hard Rock Cafe as the entrance to. While they're at it, get the Caddy back to be the canopy) to rejoin the purple line at Beverly/Wilshire.
Now it's not perfect. It's still not possible to get to the Valley to the beach on one train. There are no plans to put a subway under the 405 from the Valley busway to the airport, which would seem like a no-brainer to me. Some of the stops are a bit odd (16th street?), and there are going to be some big-time eminent domain issues that will have to be worked out. But in general there's going to be the main issue of getting Angelenos to actually use it. The guiding principle of the people of the City of the Angels is that we love our cars. It's our little bubble, and while we curse the traffic we are loathe to give up our bubble of AC and our own soundtrack to actually use public transport. Sure, when the gas rose to nigh unto $5 a gallon I saw more people on the bus, but that didn't last. I wonder when I hear people talking about getting people on the subway that they aren't talking about getting other people on there so that traffic would be lighter for them. Those people clogging the streets would be safely underground.
I never thought I would write this, but I'd take it in heartbeat. That is, if they can manage not to collapse Wilshire the way they did Hollywood Boulevard, the reason the project met with enough resistance that I'm not taking the subway to work today.