If you enter the Showcase on the Mexico side you can walk as far as Norway. Everything in Mexico will be closed until 11. In Norway, only the Akershus restaurant (you probably need a reservation if you're thinking of eating there) and the Frozen princess meet and greet are open, everything else is closed until 11. You will be blocked from proceeding past Norway.
If you enter on the Canada side, you can walk through the Canadian, British and French pavilions. The only thing open before 11 in any of them will be the bakery at France. You will be blocked from proceeding past France.
It's worth noting that the pub in Britain and Tutto Gusto in Italy open at 11:30 and La Cava del Tequila in Mexico at noon - they don't open at 11 with the rest of the showcase.