I am a bit perplexed by the RAVE reviews here on Hotel Alcantara. I think it's fine, but it definitely is a 2* no frills hotel. One review even called it a "boutique" hotel - hardly so.
I stayed in a single room for 2 nights. The room is the smallest single room in Spain I stayed at during my 12-day trip (on which I stayed at 4 different hotels). Bed is a twin bed and bathroom has shower stall only. The room is clean but my bathroom had a faint sewage smell. I was too lazy to ask to be moved, so I just left the bathroom window open and the bathroom door closed during my stay.
There is a TV but I couldn't find any English channel. There was no remote control in my room but I kept forgetting to ask the front desk about it.
There is no in-room safe, but the reception area has several safes where one can put their valuables in and you keep the key with you.
My room faces the inner courtyard and is very quiet at night. No one ate breakfast in the courtyard during my stay (it was Feb) but potentially it can be noisy in the morning when it's warm outside.
I liked the location and it's fun to wander around Barrio Santa Cruz. The walk from the Prado/Sebestian bus station is about 12 minutes w/luggage, 10 minutes w/o. There is no easy way to get to the Santa Justa train station by public transport, so I took a taxi. It was a short ride and cost €5.
Breakfast buffet is simple but a good price at €5. It has cold cuts, cereal, breads, juices, coffee etc. What it doesn't have is hot food.
The front desk staff is really awesome. All are cheerful and helpful and very nice. I met the staff from all 3 shifts and everyone I encountered was just great!
The bottom line: I think I will recommend it with some reservations. For the price they're charging, you may be able to find somewhere else a bit more luxurious for just a few extra more euros.