Hi, and thank you for your interest!
Budget Blitz is being translated using Weblate, a web tool designed to ease translating for both developers and translators.
Translation project for Budget Blitz into Spanish currently contains 838 strings for translation and is 46.1% complete.
If you would like to contribute to translation of Budget Blitz, you need to register on this server.
Once you have activated your account just proceed to the translation section.