I'm going to Ecuador for about two weeks. I'm planning four nights on a Galapagos cruise. The remaining 10 nights would be split among Montanita, Banos and Quito. Is that enough time to spend in those places? Any other suggestions? Is Montanita recommended?

Anything less than a week in the Galapagos is money poorly spent. You lose the better part of your first and last day there, so it is really only 2 full days. We were in the Galapagos for 10 days and it was barely enough.
Regards,
Bob

Montanita is a party village on the coast. Banos is a party town and adventure/outdoors area in the Sierra. Whether they are recommended depends on what it is you are looking for. 10 days between Montanita, Banos and Quito is doable, but you will spend about half your time on buses.

Either spend at least a week on Galapagos and the rest Quito/Banos or Quito/ Montanita... Personally I would spend it Quito/ Quiitoa Loop for a less touristy experience....

I am looking to do some partying. As I plan out an itinerary, I see what you mean about the buses. Is it possible to get from Banos to Montanita in one day, assuming I fly from Quito to Guayaquill? Do you think 5 days and 4 nights is too little in the Galapagos given the amount of time I have in Ecuador?

Do you have any flights booked yet, including your international flights? If so, where are you flying into and out of? Given the cost of getting to and around the Galapagos, it really doesn't make sense to be there for less than a week, but if you really want to travel somewhere else as well, you don't have much choice.

I don't have them booked, yet. I'm trying to sort out the days given the various cruise options. Is it possible to get from Banos to Montanita in one day? What about the Galapagos to Banos in one day? Thanks.

You could do Banos to Montanita in one (long) day, if you flew from Quito to Guayaquil. But in the time you have it really doesn't make sense to try and do both.
I would suggest you either
1) Fly in to Quito, bus to Banos, stay, bus back to Quito. Fly to/from Galapagos from Quito.
Or
2) Fly in to Guayaquil. Bus to Montanita, stay, bus back to Guayaquil. Fly to/from Galapagos from Guayaquil.
Option1 will also let you see Quito. Option 2 will free up time to stay longer in Galapagos.