LMFAO has hit the mainstream.  Love them or hate them (and there are plenty in both camps), the cartoonish Los Angeles-based duo’s popularity is growing with a certain cross-section of the 14-24 year-old party set thanks to infuriatingly catchy tracks such as “I’m in Miami Bitch,” kitschy You Tube videos and energetic live shows.   Redfoo and Sky Blu (yes, that’s what they go by) timed a radio hit perfectly this year with the PG-13 version of “Miami” just as an emergent pop-leaning sound was breaking on urban radio stations nationwide.  Will.i.am was instrumental in helping the act land a deal with Interscope, as the group tells URB in an interview that took place inside an infamous bi-level apartment in the Hollywood Hills where four people were gunned down in 1981 during the …