The Hilton charges $24 a night parking and the Hyatt in OC $26 which basically means the hire car will cost me $50 a day, excluding fuel. At this stage I'm thinking I'll get the car after the two nights at the Hilton and take it one-way, out to the Hyatt for the four nights then return it to LAX.
I'm not sure how I'll go driving in LA though.
Hyatt Regency OC parking charge is $22 (it just went up from $16 when I was there a couple of weeks ago).
I stay there at least 4-5 times per year (a mix of work & play visits) and usually have the parking charge waived as a regular Diamond guest (this is not normally done, but I do know of other Diamond members who have had the charge waived at check-out).
The down side with the HR OC, no regency club, however the breakfast on offer in the Tusca restaurant is one of the best I have had out of all the Hyatt's I have stayed at (both the Buffet and A-la-carte).
I assume you may be doing the Disney thing (hence staying in OC?) if so the hotel shuttle is the best option to go to the park, even if you just want to walk around Downtown Disney, it is worth the quick trip (at check-in mention you may be going to the park, they should give you a free pass for the shuttle as it is normally approx $5 per day).
In regards to food, you are surrounded with a bunch of chain restaurants, Red Robin, Outback Steakhouse, Buca Di Beppo, Joe's Crab Shack, Oggi's etc.
Target is across the road if any supplies are required (better pricing than the local Walmart for snacks and toiletries etc)
Whilst not the quickest way to drive to OC, If you drive down Interstate 5 just past the 710 interchange you have the Citadel Outlets, one of the better outlet shopping areas in the LA area.
Driving in LA is fine, just allow plenty of time, and hopefully you have someone with you so you can take advantage of the HOV (car pool) lanes... they are a god send at times.