We are having our receptiopn at American Adventure Rotunda next February. We asked the same question and were told that while there will be CM's out there directing park guests away from the AAR entrance and directing our guests in, that no they would not be able to rope off an area 'out front'. We were offered the option to have our Cocktail Hour at Italy Iosla....for the extra site fee and F&B requirements. We decided against that as most of our guests have seen Illuminations already, and it would just make the pricetag for the wedding even higher than it already is. We will be doing our Cocktail Hour on the second floor of the rotunda overlooking the dancefloor/reception area below.
As to the time you can get into the pavilion......While technically by the DFTW paperwork, you SHOULD be able to start a reception at 7:30 at the AAR, they generally try to discourage that. They prefer to book it for the 7:30pm WP slot and a 8:30pm Cocktail Hour start / 9:30pm Reception start. That reduces the amount of time that they have to shut down the pavilion / divert traffic flow for the attraction inside.
I have heard of maybe 1 or 2 brides who pressed the issue and in the end were able to get the 5:00pm WP slot and therefore an earlier start at AAR for their Cocktail Hour / Reception, but they have said that it was pretty tough to get DFTW to agree to the earlier time.
I would definitely reccommend discussing your plans with your SM/WP, if you are ok with renting II for the Cocktail Hour that's great. If not, then maybe they'll have some other creative ideas.