Within walking distance of Disneyland???... well there is Downtown Disney with Jazz Cafe ( love that place) and a number of Italian places and such but none of that really qualifies as 'street food' although Jazz Cafe has an 'express' version on the side with an abbreviated menu that basically works as such... though the quality isn't as good as inside I've found. There is also a ton of little spots just outside the entrance but most of those are also sit down...
You def want to hit up some street tacos, a chile renello plate or a good burrito while you're out here but if I'm honest I don't know the Anaheim places too well in terms of street tacos and such. If I were you I'd research places near where you are staying and find something decent. Don't trust the Mexican spots inside the parks, not very good but if it comes to that the place in California Adventure is much better and closer to authenticity than the one inside Disneyland.
Right across the street from Disneyland's main entrance on Harbour there is a lil hotel I've stayed at number of times... The Anaheim Hotel, that has an award winning pizza joint in it. I've never eaten there (it's just never worked out) but it's supposed to be very good and not too expensive. It seems as though it can be sit down or grab and go...
For cheap ass food the Captain Kid's Buffet, literally right across the street from the entrance, you can't miss it is a super cheap way to feed the family but pretty below average. It's much like the Circus Circus buffet in Vegas, pretty shitty but a good deal when everything else around you costs so much. I'm really only mentioning it for cheap breakfast that should satisfy everyone before entering the park... don't expect much other than a cheap meal.
In Disneyland the Plaza Inn is supposed to be the spot, right at the end of Main Street USA. They have a great reputation for fried chicken but I'm just whatever on it. Only place I like in Disneyland food wise is the Dole Pineapple place and the Bengal BBQ just across from Indiana Jones (Both these posts are in Frontier Land just FYI) . Bengal BBQ is one of the cheaper places to eat too...
Might need an Uber for these but worth mentioning:
I'd highly recommend the Karl Strauss brew house across the street from Angel Stadium (about a mile or two from Disneyland) for great food and good beer.
There's a decent German spot right off the 57 fwy (Ball Exit) called Jagerhaus.
There is also a Roscoes Chicken and Waffles on Harbor down the street from Disneyland... not quite walking distance but a very short drive away. Always good stuff there and you can say you've been...