In 1999 a default judgement was entered against me for tuition. The summons was left in the foyer of my apartment, I never signed for it. Do I have a case for improper service to have the judgement vacated?

Unlikely at this late date. Even if you did get it vacated, you would be served properly before you left the courthouse. So, if the debt is valid all you would have done is delay the inevitable.

If other attempts where made, ( number of attempts) and obviously you got it, since it was left there and you know it was, so I guess it worked ?

But if they meet the other requirements to be allowed to put it on the door, then yes it would be legal.