This festival takes place between 2nd and 13th June, in Mogan. The last day is Monday 13th June, so most public buildings (like the town hall, banks etc) will be closed, although it takes more than public holidays to close most of the tourist shops and restaurants.
This is just a small local fiesta so everything outside Mogan should be open for business as usual.
Between 11am and 2pm there is a gastronomic fair with cheese, bread, nougat, wine and more. There is a Eucharist at 11.30am. At 9pm there is a gala in the municipal park which you might like to go and watch 😀
You can find more information about this festival here: http://mogan.es/Agenda/2011/05_Mayo/SanAntonio.pdf