I searched FW and did not locate this offer posted anywhere else so hope this is not redundant.

The Toll Roads (Southern California) is getting rid of the stop-and-pay-cash-when-going-through-the-toll-booth option. They are offering $10 in The Toll Roads credit when you sign up for a FasTrack or Express account. There are four options available:

FasTrack: You get a transponder. Charged a $2 monthly maintenance fee. Requires a minimum of a $30 deposit into your account at sign-up.
Express Account - Prepaid: No transponder. You prepay the card and it is debited each time you drive on a toll road. No monthly maintenance fee assessed but you must add a minimum of $30 to your account when you sign up.
Express Account - Charge: No transponder. You give them your credit card number and they charge it each time you drive on a toll road. No monthly maintenance fee assessed. Does not require any upfront money paid when signing up for an account.
Express Account - Invoice: No transponder. They bill you monthly by email or postal mail and you send in payment or pay by credit card, etc. $2 monthly invoice fee assessed. Does not require any upfront money paid when signing up for an account.

I signed up through this link and saw a $10 credit immediately displayed in my account.

For existing or new The Toll Roads members considering signing up for a new Orange County Register newspaper subscription, you might want to sign up through this link instead which will give you $50 in The Toll Roads credit. That page also details a Costco deal on transponders as well as a deal with Albertsons and The Toll Roads.