I'm just walking round some beats
Tongue in cheek, just talking round some teeth
Lupe is referring to George Zimmerman, the man who was acquitted of multiple charges in relation to the death of Trayvon Martin, who he mentions a couple lines from now.
He was a former neighborhood watch-captain who kept an eye on his area for any type of criminal behavior, which he suspected Trayvon of being involved in.
“Walking a beat” is patrolling on the job, usually as a police officer or a security guard.
Also as a continuation of the previous lines, Lupe could be walking around casually wearing some Beats (by Dre headphones). This would also tie in with the “neighborhood hoodie” line which follows in that he is both walking around casually (minding his own business) and walking around casually (dressed casually in a hoodie rather than in formal attire).
In the line about walking around beats he actually puts the word “beat” off beat. So he is actually rapping round the beat (off beat), not on it.
Lupe is just having fun and giving a subtle wink to his fans that he’s not taking this or himself too seriously.
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