Yes, you can purchase 3/4 hopper tickets if you stay at the three Disney Resort Hotels (MiraCosta, Ambassador &
Disneyland). I can't remember if they offer 1/2 day hoppers for resort guests. A 4-day hopper was an additional $60 USD for two adults and two children over the regular 4-day ticket. We splurged for this option; however, having never been to either resort before, we didn't hop the first two days.
We found that takes about 30 minutes to hop between TDL to TDS and about 20 minutes from TDS to TDL. Either way, we did park hop later as we knew which attractions we wanted to ride again, restaurants to eat at and shows to watch.
Each park can be enjoyed within a single day; however, you'll find restaurants to try that would take longer than 4 days. Also, don't forget to allow time to shop in either park or outside at Ikspiari or Bon Voyage (we never made it there ourselves).
With all this said, I'd recommend saving the extra money for park hopping the first two days and spend it somewhere else.
Either way, you will enjoy the time in both parks and don't forget the popcorn

(both parks have the same flavors; however TDL has a Star Wars Bucket while TDS has a Duffy Basket). We didn't buy either, just a round Mickey Mouse bucket, Lavender Minnie Mouse Bow & Little Green Men (Toy Story).