Just ordered an XL pizza with delivery and 2$ tip for $6.50 (w/o would be $1.50). Bellagios App registration is different than their website so even if you've ordered online you can still register! (See app in App Store)
When you register 400 reward points are instantly posted to your account and available to use.
I think Bellagio's is local to Oregon, so for must unfortunately no luck, though hoping someone finds this and gets a free (or if you like expensive or big pizzas almost free) pizza night.