For a mixed meal with tortillas, beans, rice, and toppings, many home cooks do well buying roughly enough carne asada for moderate portions rather than assuming every guest will eat steakhouse-size servings.
Short answer first
The exact amount changes if the gathering is mostly adults, if the meat is the star, or if you want leftovers for tacos the next day.
If the spread includes rice, beans, tortillas, salsa, guacamole, and maybe another protein, people usually eat less beef than they would at a meat-centered dinner. That is why portion planning starts with the whole table, not just the grill.
A party with big-appetite adults, teens, or mostly meat lovers needs a bigger cushion than a family lunch with lots of sides. Children, side-heavy meals, and midday gatherings usually reduce total meat demand.
If you decide to buy a bit extra, ask for separate packs. That way you can freeze part of the order before it is cooked instead of overgrilling everything at once.
FAQ
A small cushion is smart, especially for evening gatherings or very hungry crowds, but separating it into smaller packs helps you avoid waste.
Usually no. Young kids often eat much smaller portions, especially when there are plenty of sides.
Several smaller packs are usually easier to manage for cooking and freezing.