Dinner in Hollywood?
How early do you think?
The Hungry Cat at Sunset & Vine opens at 5:30pm.
Mozza at Highland & Melrose will definitely be open and since it sounds like you will be eating on the early side, you might actually be able to snag a reservation, or try walking in.
I'm a big fan of Hungry Cat, and as long as you arrive early (before 6:30pm) you should find a spot. As soon as 7pm hits, it's tough even for me as a solo diner to get in unless I sit at the bar (which I prefer anyway).
Mozza should certainly be able to seat you if you're arriving before 5:30pm.