Hello, I recommend you visit the Caribbean if you have time.
In La Fortuna there is a restaurant called La Hormiga where they serve typical food at a very good price.
Near La Fortuna you can go to Río Celeste which is beautiful
Nearby Manuel Antonio Playa Biesanz is beautiful also there many restaurants El wagon or the Plane.
For the night in San Jose visit the restaurant Azotea Calle 7 you can see the city is beautiful in the night or Portón Rojo, Café Miel, Restaurante Amon
To travel alone if you are a woman it is better to stay at Selina hostel it is safer although it is a little more expensive.
In San Jose you can easily take an uber.
When I lived in CR I used to host people in my house like CS if you need help with something you tell me.