Q:

Could Voldemort have gotten into Hogwarts if someone inside had said his name?

Harry broke the Trio's protective enchantments when he said "Voldemort", do you think the same could have happened in Hogwarts?

A:

You-Know-Who had a spell put up so that he would know whenever and whoever said his name. The protective enchantment for Harry focused on You-Know-Who not finding out where Harry was, and not so much on disabling any physical contact.
Basically, if anyone mentions You-Know-Who's name in Hogwarts, even if his spell is strong enough for him to detect the invocation, the defenses of Hogwarts are adequate to keep him out.
In a real world parallel: If my friend checks in on Forsquare in a nearby pub, I can go to him and beat him up for owing me 20 bucks. However, if he checks in at Area 51 military base, I can't, even if I know exactly where he is.

