Okay, so I have been invited to attend at wedding. I am the "and guest." I don't know the people who are getting married and I'm not certain at this time, in the process of finding this out, how formal or not it is. But assuming it's not black tie (I'm covered if it is) nor casual, I have a light material, blue and green large print flower dress. It's empire waist with a cris-cross top. Would this be okay for 6:30 pm? Suggestions? Like I said if it's black tie, I have a dress for that. I just don't know if this would be okay if it's not.

I am not sure of "proper etiquette" of a wedding, but I do know that I am also getting married in a month at 6:30 PM...
I am having a black and white wedding, just for the bridal party though. I know that if someone shows up in black I will not mind at all. What you said you have sounds great... besides I am more of a "whatever you are comfortable in" type... either or will be just fine.. and that is from a brides point of view!

The non-guest isn't aware what sort of attire would be appropriate?

He would be the first person I would ask.

I have asked the person I am going with and she is going to find out. I just want to be prepared either way, in case I need to go shopping for a different dress. I was concerned about the flower print after 6:00.

I think it would be appropriate. If you had a solid colored shawl to cover your shoulders - evenings may get chilly - that would only add to it.

Is the wedding in a "tropical" area? Or is it more Northerly? If it was in, say, Florida, flowered prints are great anytime.

No, it's in TN... so the weather could really go either way... all in the same day even! :-) Hmm, a shawl would be nice. I'll inevitably get cold in the evening.

Lol, I lived in Nashville for a while and know EXACTLY what you mean! :)

I'd definitely go with a shawl then. It will give you options and also keep the chill away.