WSDOT is the best place to stay informed
http://www.wsdot.wa.gov/Projects/I5/SkagitRiverBridgeReplacement/default.htmthey even have a Twitter account if you want to follow things that way.
If you are coming south from Vancouver and taking I90 east, you'll probably encounter greater delays at the border and on I405 (east side Seattle) than on the detour around this bridge. If you avoid the busiest times at the border you will also avoid the busiest times around Mt Vernon. You'll also want to check WSDOT for construction info on I90 over the Cascades. They are widening the highway on the east side of the pass.
Another option from Vancouver is to take Hwy 3 across the Cascades, and then south on 97. All border crossings on the east side of the Cascades are faster than on the west.
