I've never been to Tijuana and don't have personal experience, but I see a very different image on google maps:
In particular, rather than "an empty lot and an alley", the route passes along a pedestrian area with some trees along the edge of a car park, leading directly to a large bridge over the highway. It looks like a much more welcoming route than on your image.
Google maps is indicating that this imagery is from 2023, so I imagine you were receiving older images for some reason, before or during construction works for the path, car park, and bridge. As I said, though, I'm not familiar with Tijuana and can't guarantee it isn't the other way around - perhaps the bridge was recently removed and you have more up-to-date images of the site during/after deconstruction (if this is the case, google hasn't noticed! the curved route doesn't correspond to any physical features visible on your screenshot, but clearly follows the bridge and path leading to it).
If the indicated route isn't suitable, the bridge on Av. Frontera (slightly south of the bridge the indicated route uses) also appears to have a pedestrian path along its edge, which looks like a suitable route only slightly longer than the indicated one.