Work in IT industry needing for VISA sponsorship (San Francisco)

Hi everybody,
I'm new in this forum, thanks in advance for any reply.
I'm wondering to move in San Francisco next August/September Protected content I'm looking for feedbacks about job opportunities around SF bay area.

I'm Italian, 29 years old, I have a bachelor degree in Computer Science, 4 years of experience in private companies and research centers. In short my professional skills can be resumed with: JavaEE-webGIS development and Linux system administration.

Assuming (could I?) that my professional profile is fit for many job offers in SF:
- is the need for a VISA sponsorship too much onerous requirement to be addressed by companies?
- is the sponsorship a way that companies usually only take when the right profile for a job isn't found after several months?

My idea is to move in SF for about 2 months with a Turist VISA and start to search for opportunities on site. Other than apply for open positions and job ads:
- are there other channels to build connections between workers and companies?

Many Thanks,

Regards,
Damiano