In April of 2001, I walked up to the podium and got a table on the patio at about 7:30. It was me and a girlfriend. We did not have a PS. It was the week after Easter and not too busy. The show is worth the price of one day admission, IMO. Although you can't see the full effect from that angle, and with the trees getting so big aroung the lagoon, I don't know where the best spot to see everything is, but the patio is nice.
I understand that depending on how busy it is, even with PS at the "right time", you can ask for patio seating but it may not be available. There have been times where people who are seated inside were able to go out to the patio and stand to see Illuminations, but that is not always the case.
I have PSs for next month and am hoping for the patio. If I get it, great, if not, I love the pub atmosphere and will be happy to have a great meal there, anyway.