If you’re thinking 'Lake Como looks nice and there are lots places to fish. I'll sell it to the missus as a family holiday then sneak off...’, then you're in for a rude awakening. Firstly, you aren't sneaking anywhere - getting around is a nightmare. The roads are only a couple of centimeters wide and the entire area is served by around seven parking spaces, five of which will only fit a 1987 Fiat Uno. Locals treat the roads like a racetrack and tourists refuse to go over 5 mph. It's also beautiful and there is a lot to do. There are cafes, bars, restaurants, boat trips, scenery and the climate is lovely. The food is great and the locals are friendly and relaxed. Finally, if you do go your flank will be under constant attack with requests to go to Milan for shopping. Fishing? Fat chance.
Access to Lake Como itself can be difficult as it is bordered by private houses. It turns out Clooney has a place not far from where we stayed (in a cheap Airbnb). George made the rookie mistake of getting himself pap'd in a local restaurant which led to my wife 'researching' on the Internet and discovering his house. Anyway, I'm getting off topic; my point is that if you are going to fish Lake Como you have to pick your spot. Between the lake-side residences of the rich and famous, there are parks and harbors. It drops off quickly and the water is choppy so wet flies and, temperature dependent, possibly a wet line are best. Popular patterns are palmer styles such as Bibio, Zulu, Soldier Palmer, Black Pennel, Black and Peacock and Red Tag as well as spiders like Partridge and Orange. You can get permits from local tackle shops.
If you have bigger cajones than me, your other option is to go to rivers and lakes in the surrounding area, but, like I said, this would take the whole day. I would go again, but I would forget any fantasies of going fishing and forgo the hidden tackle. (The stress of getting found out was too much alone) and just enjoy the break.