The first sign of a shady agency is if they ask you to sign a non-compete agreement. Legit agencies draw talent by valuing them and building good relationships, the shady ones try to intimidate you into sticking with them so they can milk you for as long as possible.
1) TalentBurst has a non-compete that's much longer than average -- you agree not to work in any capacity for your client until after a year from when you left. I've never seen these things longer than 6 months. If you've been around, you'll know that you can just walk out and find many agencies who have no such agreements. Recommend you do.
2) No, non-compete's aren't enforceable in California. But TB has a clause that any dispute has to be taken up where their HQ is located, Massachusetts. So you'll have to agree to take off work and travel to a judge there if there's an issue.
3) And Mass judges have a history of backing non-compete agreements. You'd probably still win if you did all your work in CA, but you'll have to wonder about it while you're taking off work and buying plane tickets and hotel rooms. Can you afford it? Are they betting you can't so you'll submit and avoid the mess?
4) Do a search, TB has a history of going to court over these things. Recently they sued a former client who hired someone who'd signed their non-compete. And more incredible, the founders of the company were sued by their former employer when they all broke off to start their own agency and took the clientele with them. It's like a TV show or something.
5) The result of the above is that to work for them, you have to sign an agreement that can be used to pressure you -- with economic fear -- into refusing an offer from your client that in CA you have a legal right to take. And they can use it to worry the client enough to rescind an offer. Not that they can win any court cases, but if they show up with your signed non-compete and say they're going to fight, how many employers won't simply say 'too much work, nevermind'?
You can go to about any agency at all and avoid all this mess. Your choice.