There are three different sections of "West Irvine" which are all distinct.
Section one is what people commonly refer to as "West Irvine." It is bounded by Jamboree, the 261, Irvine Blvd, and Trevino, and is within the HOA zoning. All of the condos and SFRs here pay $55/month for community upkeep, which includes mainly the community pool, tennis courts, landscaping, streets, and lighting.
Section two is actually called "Independence" and does not have an HOA. It is the section bounded by Jamboree, the 261, Trevino, and Portola. There are a couple of parks, which are city maintained, but residents in this section do not have access to a community pool.
Section three is the only gated section of West Irvine, and is called "Sheridan." the boundaries of this section are Portola, Jamboree, the 261, and the OC Fire Authority Facilities. HOA dues for this section are at $140/month for the master since there are fewer homes to spread the fixed costs over. Sheridan has its own pool and amenities within the gates.
I am admittedly biased towards West Irvine, as I live, own, and specialize in this area. If you've got questions, feel free to PM me.
-IrvineRealtor