Coincidentally, there was already a post here about this, but I've just edited all info on the CSI pages referring to Cyber taking place in Quantico. Krummy and Elijah explicitly stated that they were based out of Washington in "Hack E.R." (Krumitz: 'I thought Avery grounded you' / Elijah: 'We all know Baltimore is just a suburb of the District'), before this there has been an onscreen reference to them being in Washington during every episode, as well as the Lincoln Memorial being featured in episode 1, and the Washington Monument in almost every episode. 

 I'm just posting this here in case anyone is still adamant it's set in Quantico.