First off, this creek is not located in Boston Bar, but rather on the Coquihalla Pass. Second, it doesn't rate well as a creeking run, but has a decent park and huck drop.
Now that that's out of the way, when should you go? Early in the snowmelt season (May-June), as the Coquihalla snowpack does not last long. There's no gauge on the creek, but a good target flow could be 15cms on the nearby COQUIHALLA RIVER BELOW NEEDLE CREEK (08MF062), or 100cms on the more commonly referenced COQUIHALLA RIVER ABOVE ALEXANDER CREEK (08MF068). It's a small creek so it needs a pretty healthy flow to be paddleable, but not full freshet due to the amount of wood.
The creek is located right next to the Coquihalla Highway as it climbs towards the pass, about 30 minutes northeast of Hope. The trickiest part of shuttling is dealing with the high speeds and controlled access points of a freeway. For the full run, put in at the Box Canyon chain up area, and take out at the Portia U-turn (Exit 202). You might have to drive further along the highway and use U-turn exits to make this happen. It's possible but a bit sketchy to stop across the highway from the best drop, at an unsigned gravel pullout ~10km southbound from the Zopkios Rest Area, just downstream of where the highway crosses back to river right. There may be an old "Iago" sign on the northbound lanes which are next to the river, but there is no great pullout on that side.
The best part of the run is a bedrock ramp into a 5m falls, ending in a huge pool. The rest of the run is not recommended. It's a mixture of bumpy rapids, logjams, a couple cool tunnels under the highway, and the occasional bedrock ledge. If you want to try any of it, perhaps try the lower half as there is a bit more water and bedrock.
Below the Portia take out, the creek is reportedly too steep for kayaking down to the confluence with the Coquihalla. The section of the Coquihalla River from Coquihalla Lakes down to this confluence has been run and is not worth doing (IV+ (P)).