I would love to return!

tl;dr If you're hesitant about going, go. This was safe and a truly unique experience, and I had a wonderful time.

This program is great! Here is a general idea of how the days went:
Monday-Friday: 8am breakfast, 9am-noon Spanish classes, noon-1pm lunch, rest of the day is free (sometimes there were guided excursions at various times depending on the activity).
Weekends: Breakfast and lunch provided but otherwise on your own.

Food:
I have a sensitive stomach and was concerned about not having a lot of control over that. The staff is extremely accomodating and I did not have any tummy troubles in my week there! I'm lactose intolerant and do not eat red meat, which they easily accomodated. There was another person there who had Celiac's, and she also did not have any issues. They have filtered water available as well. I brought a Life Straw but didn't need it.

Lodging:
While I was there, everyone else had paid to upgrade to private rooms so I ended up having a private room myself! There is AC in the rooms which I did not know about the first night. They provide you with a basic pillow, fitted sheet, and flat sheet. I can't imagine sleeping with more than a flat sheet given the heat though. There is a small lock box for your belongings and a space to hang your clothing. The door of the hostel is always locked and there is always someone on staff, so I never felt like any of my belongings were at risk. There are multiple toilets and showers available to use, but bring everything you will need (they provide a small towel).

Spanish:
We took a placement test on the first day, which I was excited about. Because there weren't a ton of people during my week, we all had one-on-one lessons which was AMAZING. Everything was catered to my ability level. I took Spanish for several years in high school (and have a bachelors in linguistics--I'm a dork), and the amount of latent Spanish I was able to revive in this week was truly astonishing. I loved my lessons so much.

Staff:
The staff here feels like one big family. They speak varying degrees of English, but if you don't speak Spanish, you'll usually find at least one person who can act as an translator if need be. You can also practice your Spanish with any of them judgement-free. They truly made me feel so welcome.

Transportation:
Biggest recommendation besides to do this trip is to pay for the add-on for transportation to and from the airport. I like to travel and would never opt for this service, but it was so nice to have one less thing to worry about. Also, it was the only cab ride where I didn't get ripped off. There are no meters like we're used to in the US and they will overcharge you if you're a tourist (which ends up still being cheaper than an equivalent ride in the US).

Internet:
Assume you will not have access to internet. The wifi at the airport does not work. The wifi at most places that have wifi did not work for me. My understanding was that SIM cards could only be purchased with a credit card, and they do not take American cards. We were lucky to find a bar that had outstanding wifi and I used that to contact my family and check my email.

Safety:
I felt safe for the entirety of my stay. There is a ton of catcalling but it doesn't go beyond that. If you look like a foreigner, you will be approached often and people will try to scam you. People are not forceful though and you can always walk away. I had a cab try to overcharge my friend and I once after we had pre-agreed on the amount and we said no and were able to leave the cab. I wouldn't walk around late at night but yourself but I wouldn't recommend doing that pretty much anywhere. LIke I previously stated, the hostel itself is extremely safe as well.

Other info:
-Do your research beforehand. Assume nothing you need will be available here (shampoo, soap, tampons, medicine).
-Bring a small first aid kit. My must haves were aleve, claritin, and an anti-itch cream (I got quite a few bug bites).
-I went the first week of June. This is the off-season for tourism as it tends to be excessively hot and humid, and is the start of hurricane season. If you come during this time, bring more clothing than you will need as you will sweat through just about everything. (Also, I would honestly consider returning during this timeframe because despite how terribly hot it was, there are less people)
-Wait to exchange your money until you get to the hostel. Make sure all of your bills do not have writing or rips/tears.
-Download maps.me and download the map for Cuba so it will work offline.
-I booked some afternoon excursions through Airbnb and was so glad I did. The excursions the staff offers are great, but if you're looking for something more specialized, you can book it yourself. Make sure you do this all before you leave, as you will likely not be able to access Airbnb while you're in the country.
-Make sure to bring donativos!
-If you're a light sleeper, maybe bring earplugs.
-While it is safe, leave your jewelry or nice handbags at home. Cuba is extremely poor and it just looks like you're flaunting your wealth. I saw people (not in this program thankfully) doing this and it was embarrassing.
-Have an open mind and you will have a fantastic experience!