I had an incredible time in Alicante over the summer. I grew a lot in both personally, in my own independence, and in my Spanish-speaking skills. Alicante is incredible. The school where we attended classes was a 5-minute walk to the beach. Every afternoon there was some activity planned, like doing a city bike tour or beach volleyball, and every day it was different. On the weekends there would be bigger outings planned, such as spending a day visiting castles and waterfalls.
Alicante isn't a really well-known city, which was initially unappealing to me, but I think it was a better choice than a big city would've been. We had a weekend trip to Madrid, and I realized that being in a bigger city had a lot of potential for things to go wrong... a lot more theft and crime occurs in more prevalent cities.
The classes were intriguing and my professor was really fun and made class actually appealing. I liked that we not only learned about the language but also about the culture of the place we were staying in. Often, our afternoon activities would be catered to what we were learning about in class, which made my learning experience so fascinating. I'd taken 3 years of Spanish prior to the trip, (the requirement is at least 2) which I thought would suffice, but it really wasn't enough. A lot of the 40 kids on the program were nearly fluent, having spoken it from childhood. And instead of there being 4 different levels of class intensities as advertised, there were 3 classes: 2 for advanced kids and 1 for not-advanced, like me:). So for that reason I'd recommend 3+ years of Spanish unless you regularly speak it. Without a roommate with me in my host home, I would've had an extremely difficult time trying to communicate with my host mom. Having someone who also spoke English kept me sane when I didn't understand anything.
After class each day, you'd go home for lunch with your host family and take a siesta, which would be a couple hours of downtime, where you could really do whatever you wanted: do your homework, take a nap, watch Netflix, go to the beach, go shopping, etc. The siestas were some of my favorite times on the program because it gave me time to just chill out, especially when we had busy days, or do something with my friends. But I was really impressed with CIEE for the level of planning and preparedness they orchestrated for our afternoon activities and weekend outings. There would always be a perfect balance between downtime/free time and planned activities.