In short, the location matters, as it can definitely increase your exposure to Tech industry clients. Yet, it's typically also not a deal breaker, if you're not part of such location.
To share a bit more context, BCG in the US is is organized into regional systems - North East, Great Lakes, South, West Coast. Generally speaking, these systems share common staffing pools, from which projects in the region primarily staff their consultants. Hence, being part of a system that has higher abundance of Tech clients (e.g. West Coast), you will find it a bit easier to get staffed on those accounts. I'll re-emphasize here we're talking about system-level, rather than a specific office (e.g. West Coast includes SF/SV, LA, Seattle, San Diego). So if you don't like being in SF particularly, should not be an issue.
Now that said, even when you are not part of such system, you will still be able to do Tech work - in, reality (esp. in the US), it's often about who you know. Esp. during Covid days (-> remote work anyway), I'm hearing that staffing has become quite a bit more flexible in that respect. Just takes a bit more networking effort upfront, to get the same exposure.
Hope this helps - feel free to PM if you have further questions.