I know this was posted a week or so ago - hopefully late is better than never.
I rode the trail from UNM to Pennsylvania the other day, and it's all clear.
AFAIK there's no pending construction along that route - it's fixed at San Pedro where they were doing the San Juan water project, and I don't think they'll be tearing it up again.
The route you describe takes you pretty far north. Constitution might be an alternative; it has a bike lane, although it's pretty narrow in places and winks out of existence at most of the stop lights. You'd take Washington (or perhaps Girard, depending on where you're located) to Consititution, and take that all the way to the east side of Louisiana. Then take smaller streets (San Pablo to Marble would work) to drop down to Marble, and take that east to Pennsylvania.
Another option might be to take Campus east. It turns into Copper when it crosses Carlisle; if memory serves there's a bike lane when it's Campus, and it's fairly lightly traveled but with no bike lane where it's Copper. It ends at San Pedro (the fairgrounds are right there), but you could take San Pedro north to Marble (no bike lane and a fair amount of traffic, though). Marble is more or less straight from San Pedro to Pennsylvania.
HTH!