My family’s favorite fast Mexican joint, Poquito Mas, is just across the 101 from Universal. It’s a chain, but a very small LA-area one. The food is more Cal-Mex than pure Mexican, but it’s fresh, made in front of you, and won’t come anywhere close to breaking the bank. It’s a hole in the wall with limited seating inside (there’s also an outdoor patio) and it can get crowded but service is fast.
https://www.poquitomas.com/location/studio-city-the-original/
if you want an old Hollywood experience, the Smoke House is across the street from Warner Bros Studios and has been around since 1940s. It’s a decent steakhouse, but real draw is sitting in part of movie making history (for example, George Clooney named his production company after the restaurant)
https://www.smokehouse1946.com/
Another local institution since the 1940s in Miceli’s, next door to Poquito Mas. It’s typical Italian restaurant food but the draw is the singing waitstaff, from opera to Disney show tunes to standards. It’s LA, so the quality of the talent is pretty great if you and your tween are up for some entertainment with your meal.
https://www.micelis.restaurant/
The neighborhood of Toluca Lake is just down the hill from Warners/Universal and has lots of restaurants, from quick service to fine dining. Riverside Drive is the main drag. The oldest remaining Bob’s Big Boy is at 4211 Riverside and has been restored to its 1950s glory; they even have car hop service on weekend nights and a classic car show on Friday nights. Drew Carey likes to sit at the counter and the restaurant has been featured in various films. The food is classic diner and burger fare; it’s usually decent. Breakfast is good, if you like diner breakfast.
https://bobs.net/
These are the more unique-to-LA places that I can think of, but if you’d like more upscale and/or foodie recommendations let me know! I used to live and work in the area and I’m there often.
if you go to Porto’s - which is delicious! - be aware there is often a line, depending on time of day.