Our only other choice of a month is January, and that seemed silly for Friuli --- January is better saved for our return trips to Venice and Florence to avoid the crowds. We love Italy in both April and November, so do you know of reasons why one month would be better than the other in Friuli?
Our interests are local food and local wine, pre-Renaissance art & architecture, ancient Roman sites, odd little museums, boats, wildflowers, food markets, festivals, and just driving around. Husband also enjoys opera and cooking classes. We don't need to see any more of the Dolomites. Maybe just two weeks?
So far, here's where I think we'd go in the area:
Aquileia of course
Cividale del Friuli for the 8th century Tempietto Longobardo, the Museo Cristiano del Duomo & National Archaeological Museum, the Ponte del Diavolo (we collect Devil's Bridges)
Sesto al Reghena for the Abbey of Santa Maria in Sylvis church frescoes
Spilimbergo for the Scuola Mosaicisti del Friuli
Udine for Church of San Francesco
Trieste for the Cathedral of San Giusto, the WWII museum Civico Museo della Guerra per la Pace, and a bunch of other stuff
Gruaro for the Church of San Tommaso Apostolo frescoes