Mal,
If it's a afternoon outdoor wedding, mid 70s weather, I might wear a nice skirt/blouse combo or perhaps a semi dressy suit. Probably in a light color, considering the time of year/weather. Maybe a pretty, strappy shoe too. Especially if the reception is indoors at 5 PM.
I certainly don't think long is appropriate unless it's something lightweight and flowery (rather than a gown style). And stay away from heavier fabrics and darker colors. I would think light and bright. Of course, if you have time in between the ceremony and the reception, you can always change into something more dressy, depending on whether this is Saturday evening or not (I think Sat evening requires something dressier).
What types of conflicts are you hearing from people? I'm on the East Coast and made the mistake last year of wearing a black, just under the knee dress (sleeveless) w/ an attached long jacket to a July wedding (it was indoors but the ceremony was outside on the pier). I was so hot and since the jacket part was attached, I couldn't take it off. I should have gotten a nice skirt and top w/ a removeable jacket and I would have been better off. This was at a fancy restaurant with a view of the NY skyline, just to give you an idea.
Hope you find something you like.
