My suggestion would be to visit Mallorca for more than a few days, but, if all you have is a weekend, below are my recommendations to maximize your time.
If you want to stay in the Santa Catalina area of Palma de Majorca, I'd recommend Hotel Saratoga. It was clean, modern, comfortable and affordable. The staff members were accommodating and the facilities were more than adequate.
Get up early (by Spanish standards) on Saturday morning and go for a stroll by the harbor, to the Cathedral of Santa Maria, before everyone else awakes.
Then have something to eat at Cuba. It might not be a hostel nor a hotel, but is a great place for a rooftop brunch!
To walk off breakkie, stroll through the markets whilst sipping on sangria.
For sunset, take the elevator at NAKAR Hotel to the 8th floor, where the bar is situated. It is the ideal spot for a sundowner whilst enjoying the views of the city.
Have dinner at Sadrassana, in the old quarter of Palma. It's a chic combination of gastronomy and art. Get a traditional Mallorcan ‘coca’, the suckling pig, croquettes and the ceviche.
Spend at least one day lazing by the pool, listening to Balearic tunes, getting bronzed and sipping cocktails at Purobeach Palma.