The fiesta's not forever at Kensington Mexican restaurant El Gavilan, which has been driving neighbors up the wall ever since owners expanded it into a nightclub earlier this summer. Now there's dancing, music and sometimes fisticuffs! Derek Mayer, a resident who lives across the street, tells the Daily News he's been awoken at 3 a.m. with "20 drunk people congregating outside in the street." And in May he saw a knife-wielding man trying to slash a bouncer armed with a baseball bat. After some pressure from Councilman Bill de Blasio, the NYPD raided the place at the end of July, citing the owner for selling alcohol after hours, unlicensed sale of alcohol, operating an unlicensed dance hall, employing an unlicensed security guard and serving alcohol to minors. But the owner's brother insists El Gavilan is "not a discoteca. The people come, they listen to music from the machine. There's no live music." Live or not, the music's too damn loud, counters Albermarle Neighborhood Association President Larry Jayson. And don't even get him started on all the horn honking!