First & foremost, keep in mind that standards for a 5x/week drama differ from those for a once a week series or a one-off movie. The quality of the scripts, acting, and production for a daily series will suffer a lot more lapses, ups & downs than other TV shows. Having said that, I give Derecho a soñar a high rating because as daily dramas go (what used to be called "soap operas"), it's one of the best I've seen.
The central character is Julia, who starts out as a stocker in a supermarket, until she quits because her boss sexually harassed her. We later find out that Julia is actually a lawyer, or at least got her law degree in university. Desperate for work, Julia applies for a position at a law office, but by a twist of fate, ends up getting hired as a secretary for one of the partners.
The other protagonist is her boss, Jorge. After spending the last few years in Chicago, he is new to the firm, taking over as a partner due to his father's unexpected death. Jorge thought he would spend a week or two at most to sort out his father's affairs, but the circumstances of his father's death are far more complicated than he or anyone else expected. Jorge ends up staying in Spain, leaving behind a fiancee in the US and embarking on a new life in Madrid.
Derecho a soñar reminds me of a madrileña version of LA Law. While we see some courtroom action, much of the drama takes place behind the scenes, in the office and in the personal lives of the characters. Considering the tremendous undertaking of 5 hour-long episodes a week, Derecho a soñar does a commendable job of maintaining the quality of its scripts & storylines.
Final note, for viewers whose speak Spanish as a 2nd language, Derecho a soñar is a great show to watch. While the dialogue is typical of the way madrileños speak nowadays, it's not packed with slang or ridiculously fast. Better still, subtitles (in Spanish) are available in case something flies by you.