HELP - can i complain about the smell thats invading my home from my next door neighbours?

In California, you can call the local county offices and they will send someone out to inspect. Also, you can take legal measures as any noise, (not sound, real noise) and/or smell and or activity that crosses into your property is legitimate grounds to file a complaint. Start with downloading the appropriate form at your county offices, then go to police and housing authority. It will get checked out and if it is the building or tenant, you and the building can take action from there.