Probably not! There are no CMRS licenses available for that market, and it's extremely unlikely that an existing licensee would part with one of their licenses.
However, as others pointed out, metroPCS does have 20 MHz of spectrum for the greater Los Angeles area (10 MHz PCS C5-block plus 10 MHz AWS D-block) and is supposed to launch service this Spring.
Since Cricket and metroPCS usually don't compete in the same market (with Merced and Modesto being the only exceptions to date), it is possible that they will allow customers to roam on each others' networks. It is also possible (and would make a lot of sense due to economics of scale) that the two companies merge at some point in the future and corabine their license holdings and service offerings.
Even if they don't merge and don't forge a nationwide all-inclusive roaming agreement, it's still quite possible that metro and Cricket will roam off of each other in CA, seeing that Cricket kind of has metro surrounded (metro has LA/Bakersfield and SF Bay/Sacramento and Cricket has San Diego and the central valley).
