With the amount of time that you have I don’t think it would be unreasonable to drive to Cuenca and back if you’re interested in seeing that city. I wouldn’t bother with Guayaquil as it takes more time and isn’t that attractive to most expats. If you do go to Cuenca allow for a full day of driving each way. Or maybe stop in Baños overnight on either the way there or back.
If you just want to do short trips out of Quito I would definitely recommend hitting the Otavalo/Cotacachi area. Saturdays are the big market day in Otavalo and that’s always a fun time so you may want to schedule your trip up there around a weekend. Mindo is in the cloud forest and only a couple of hours from Quito. And I already mentioned Baños which is a few hours south. I definitely think Quito’s valleys are worth exploring too and that can keep you busy for a few days.
I hope this helps and let me know if you have any other questions!