Baidu's "Wikipedia" gives us some clues on how to translate 城管:

① 名词：以暴力手段维持形象，专门欺压租不起商铺、办不起执照商贩以及其他弱势群体的黑社会组织。例词：城管上道，鸡飞狗跳。
② 形容词：形容残暴、血腥、恐怖。例句：你也太城管了！
③ 动词：等同于打、砸、抢。例句：他不老实就城管他一下！
④ 叹词：无奈之意。例句：这世道，城管！
⑤ 代名词。例句： 关门，放城管。

① noun: a mafia-type organization devoted to keeping up appearances through violence, exclusively bullying those who can't afford to rent a storefront, can't afford to register a business permit, or belong to other disadvantaged groups. ex: the chengguan are on the prowl, everybody scram!
② adjective: violent, gory, horrendous. ex: That's too chengguan, man!
③ verb: same usage as beat, smash, take by force. ex: If he misbehaves on ya, just chengguan him a bit!
④ exclamation: a feeling of helplessness. ex: What a world... *chengguan*!
⑤ pronoun. ex: Lock them out and sic the chengguan (dogs) on 'em.

Personally, though, I'm favoring "beat patrol".