MKM
On call interpreters. Any city with a large Spanish speaking population probably has them.
Or, AT & T offers a 24/7 service with interpreters that speak any language. You call one number, tell the operator what language you need, and within minutes there is an interpreter on the line. With wireless technology, that is not too difficult.
And even if it takes an extra half-hour to an hour waiting for an interpreter, I think it is worth it. The driver's constitutional rights are protected and the prosecution will most likely get a conviction.