Tacos Juanita's is a taco truck on the corner of Broadway and Marineworld Pkwy in northern Vallejo. It seems to be there for lunch trade and stays until about 9pm. There are a couple picnic tables for dining al fresco and a canopy to shade the sun.
With three visits under my belt here, the taco I've liked best is the one made from chicharrones, deep-fried pork skin. Crackly crisp with lots of bubbles, not the hard kind, this one starts out with a swab of refritos on the tortilla to hold them on the diced cubes of pork rind. While the tortillas here are thinner and not as intensely corny as the trucks in Santa Rosa use, Juanita's compensates for that by adding a bit of grated cabbage and a slice of buttery avocado to top each taco. A balanced meal for only $1.25.
The other tacos I like are the carnitas and the buttery lengua. The tamales were made with pork and were the fluffy masa genre, but don't seem to be available anymore. The salsas are very good here - a tomatillos/avocado one with mild spice and a tomato and other veggie cooked salsa with medium heat. Hot red sauce is available if you want more heat. You help yourself to the sauces and to the pickled jalapeño peppers.
On weekends, the menu says they have tacos de buche (soft and chewy pork stomach).