I feel you OP, I recently had a somewhat similar situation. When we were moving into our apartment, I walked around the corner of my house to see 2 meth head fuck wads, one standing on my porch and one halfway in my house with the door open.
I thought it was my girls little brother at first (he was on his way), but when I realized it wasn't him I was like wtf. They tried being all buddy buddy with me (pretty sure they smelled the bud, don't think they were smart enough to know it was a grow tho, they were just trying to get me to smoke or something). So anyways, I wasn't having it and told them to leave in a pissrd off manner, but was still as nice as i could be.
My girl came to the door and I kinda slammed it, told her what was happening and she asked where they came from, I was like "well I asked where he lived and he said in a house that way-" I opened the door to show her the direction, and the fuck wads were still standing there, like a full 60 seconds later..
That's when I got fucking pissed.
I'm not humongous by any means, but im 6'2" and weigh about 190. They were both smaller than me so I shoved one to the ground and got in the other dudes face. I yelled, asked him if I wasn't fucking clear about him getting the fuck out of there, yadda yadda. He got this relaxed, sleepy face and I couldn't tell if he was just trying to keep his cool while hia buddy scurried off or if he was just fucked up on nerve pills or something, but he just kind of stood there while I cussed him. Finally I pulled my hands up in front of his face and said, "do you see me fucking shaking? Im trying like hell to keep from knocking you the fuck out, you need to just leave". I went back in and he left, but I couldn't shake the situation.
I couldn't call the cops bc I was harvesting my OG and had half hanging in the closet, and that bud was so stinky there just wasn't anything i could do about it.
I thought maybe I should've just fucked the kid up, but honestly man usually that just causes more problems. You beat someones ass, and they take it as an attack on their pride (especially if you give them a nice shiner theyve got to explain for about a week) and they can easily decide they want retribution, and want to take a cheap shot to get back at you. Cheap shots are somwthing I can't afford.
I don't recommend doing what I did if its at all avoidable. If there's more of them then there are of you, then its definitely not a good idea bc shit can go waaaay south way too quick.
Honestly, if you have your grow smell under control, calling the cops might be a good idea. At the very least, its good to have cops stop by your house so that if anyone DOES go running to the police saying your growing, they will tell themselves "well I've been over there, i never saw/smelled a grow." But again, its very risky to get them over there. Luckily I had the cops over at my place right before i started growing, and after those dudes came by my house i saw the cop (who had been here before) at the gas station a couple days later, while the meth head was at that gas station. The cops were inside, but the jackass was outside at a car with his buddies. I walked up to him and was like, "you're the dude from my house the other night, right?" And he was like "yeeeeah maaaaan" and threw his hand out for a high five. I just left him hanging and said, "don't fucking come back". One of his buddies started trying to get my attention and bum a smoke but i just walked off. When I got inside, the cops were already talking about them and I was like "yeah my girlfriend was home alone the other night and I got back and those meth heads were walking through my front door. I asked if he remembered me and coning to my house, one of the women cops was like "yeah I remember your girlfriend, yadda yadda"...
To make a short story really long and then try and make it short again, basically it worked out for me, and ubwas able to kind of let the cops know without having them come by my house. BUT, the douchebags are still out there and weren't thrown in jail, and if they somehow do know about my grow then they are probably trying to time it perfectly when to rob me. I thought about getting cameras, but I'm gonna wait til my next harvest and just take the money and get a nice big place, and get cameras then.
Be careful calling the cops-- the thing about cops, is that even though they have no probable cause, their "keen sense and skill, developed over many years of policing experience" often leads them to think something is up. For example, when they think yoy are hiding something--you just pinged their radar. Like calling the police saying someone showed up at your door causing trouble, and then not letting them in your door (which I wouldn't do if you're growing).
My advice says to wait it out, get a sling shot and find some small non-lethal ammo like some grapes that won't leave much evidence, and see if they return. If they do, beam their ass in the face with a grape traveling a few hundred feet per second and see if it makes them think twice--but do it stealthily, if at all possible. Dont stir the hornets nest. Like I said, right now you are just someone to fuck with. Piss them off and they will turn "making your life hell" into their daily hobby, which definitely spells trouble for a grower.
In a nutshell--if you are pretty certain you can scare them off, go for it. Otherwise i would get a slingshot, and wait for their next move, hopefully they leave you alone.
Its so dumb--put reason number 1 million and 1 down for why weed being illegal only keeps people in more danger. Good luck with your situation man.
Be careful Calling them