Yes, it is on the block directly behind Modesto. If you go down the street leading to Santa Maria La Blanca and take your first left, it is the on the little pedestrian street with the bakery (Horno Doncellas, which has the best whole wheat bread in Sevilla.) Send me an email if you have questions.
Prices are definitely sky high for Semana Santa. Last year I arrived on Good Friday, and we had rented an apartment for 3 months. However, I stayed at a friend's for Easter weekend to avoid paying 600 euros for three nights in the apartment during Semana Santa. On the other hand, there seems to be no shortage of people willing to pay and the apartment was only a block from the Giralda, so fetched a high price. Good luck to you. If the Patio en Santa Cruz has a reasonable price, I would take it.