Is the speed of an air bubble in a fluid equal to the fluid's speed?

Mainly, they travel with the fluid, but there are some effects that have to be considered.

Air bubbles have a lower density than the fluid, so they tend to rise upwards because of buoyancy, with a speed depending on the bubble size (and the air and fluid densities). This means that in upward pipe sections, the bubbles move faster and in downward sections slower than the fluid. You know this effect from the bubbles in a glass of sparkling water rising upwards although the surrounding water doesn't.

The fluid's speed typically is lower close to the pipe surface. So, in horizontal sections where the bubbles tend to be found closer to the upper pipe surface, the surrounding fluid (and thus also the bubbles) moves slower than average.

Air bubbles can get attached to the pipe surface, creating some "sticking" effect, slowing them down or even stopping their movement with the fluid. You know this effect from some of the bubbles in sparkling water "sticking" to the glass wall.