I often check the snowpack line charts:
https://www.wcc.nrcs.usda.gov/ftpref/support/states/CO/products/#state=co&element=wteq
If you click on a region, you can see the current snowpack and compare with other years. For example, right now the melt is a little over a month ahead of the median year throughout much of the state (the black line is about 4-5 weeks to the left of the green line on the charts). So if an area is normally good to go in mid-July, then I would plan on mid-June or maybe early June. You can even view a 14ers.com trip report from a previous year, and pull up the snowpack line chart from that year (just click that year on the right side of the plot), and compare to the snowpack shown for this year. This method isn't perfect but it's what I often do (I'm interested in if other people use this approach; I'm still trying to figure this kind of thing out myself!).
As you get close to your date, you can also check satellite imagery for your specific area if you're going off the beaten path (if you have the paid version of caltopo, it includes this). Or if you're doing a very popular hike like the four-pass loop, you might get the best info from facebook groups or alltrails or the like.
But to your original question--I'm guessing that even this year, early May will be too early for most of the classic backpacking options. The Lost Creek Wilderness will probably be good to go, but I would expect it to pretty crowded (and it's not exactly what most people think of when they think of classic CO backpacking). If I were coming from out of state for a backpacking trip that time of year, I would go to UT and hit some watery canyons in Escalante or Grand Gulch or Zion area or CRNP or Paria or...