Local Beer in Italy

Can beer be purchased at most restaurants, grocery, or convenience stores throughout Italy?
Yes

Is it available in both cans & bottles?
Yes

Anybody know how much beer costs in Italy?
Prices vary depending on brand, quality, location and type of store (grocery store, restaurant, pub), just like everywhere else. Generally I pay less in Italy than I pay in the SF Bay Area at similar type of establishments/stores. I did a quick search and got the prices at UniCoop in Florence (Florence's largest chain grocery stores), you can see some sample prices of products, including beer. The attached is a little outdated (like 8 years old), I'm sure you can do a similar search and find something more updated. In any case you won't pay more that 25% above the prices you see here. Inflation in Italy has been under 2% per year since the start of the recession in 2008.
http://www.coopfirenze.it/images/prendinote/pdf/3.pdf
The above are grocery store prices. If you go to a popular fancy pub in Florence or Rome, don't expect to pay less than 5 or 6 euro for a microbrewery beer (33cl).

As Roberto said, getting your hands on Italian beer is no problem. I am not much of a wine drinker (a little white with dinner) so beer was my adult beverage of choice all over Italy. We picked bottles up from markets to enjoy back on our hotel-room terrace all the time. It's cheaper from markets than from bars/restaurants but even when having it 'out' we didn't think it was any more expensive than in the States, and sometimes less.

I don't recall ever buying it in cans, though; only bottles, and in larger bottles than in the U.S. Doesn't mean it's not possible but that was our experience. We ONLY bought Italian brands, though.

We've had lots of fun late-afternoon beers at Italian bar terraces when, after 8-9 straight hours on our feet, we couldn't walk another step!

Moretti and Peroni are available everywhere, even at small conveniences stores and they sell just 1 bottle to go.
If buying these brands costs will be similar to what you would pay in the US for a domestic beer.
If you want US beers it will be harder to find and much higher priced so really makes no sense.
Unlike most US cities/towns you can even drink your bottle of beer walking around town (I believe this is still the case, make sure to double check before you do so)

Wine is much more popular than beer so I did not see small micro brews and wide selections when it comes to beer choices, mostly just the big Italian brands.

If renting a car, beware the restrictions of allowed alcohol limit when driving is even lower than that in the US.

I'm partial to Forst, brewed in Meran in Sued Tirol.

You can still walk around town while drinking alcoholic beverages.
You can actually buy beer at vending machines like you can buy soda, however those machines require you to insert your ID card, because the machine won't dispense alcohol unless you are over 18.
The drinking age in Italy is 18 y.o. since 2011 (it was 16 before), although compliance with the law by the establishments is still spotty, in fact you can easily see 14 or 15 y.o. walking with beer cans in their hands and nobody gives a damn.
It is prohibited by the Penal code to be "manifestly drunk".
Art. 688 Penal Code:
Anyone who is caught in a public place in a state of manifest drunkenness shall be punished with a fine from fifty to three hundred and nine euro.
The penalty is the arrest from three to six months if the offense is committed by someone who has been previously convicted of an intentional violent crime.
The penalty is increased if the drunkenness is habitual.

I'd add…
Don't just enjoy your brews in your hotel room? I love Italian bars, which are not 'bars' in the American sense: they're not off limits to families, and often sell Italian sodas, snacks, ice cream and other goodies as well. Grab an outdoor table and watch the world go by! Oh, and they have them in some parks as well.

Italian brands tend to be light and fizzy - Moretti is my usual choice if they have it on hand - so you'll do fine. We did have some excellent craft brews at a restaurant/bar in Monterosso, though.

I tend to be in the camp that suggests that even though Italy and other European countries may have no "Open Container" laws, wandering around drinking is not really socially acceptable either, and being intoxicated can get you arrested.

Having a beer or glass of wine near a food vendor or as part of a picnic (assuming there are no local laws regarding eating near some sites like Rome tried to enforce) is not an issue, but recreational drinking, to drink, is not really a thing except in beach areas and other party zones.

However, you can get beer in Italy just about anywhere, if you are lucky you can find one of the few microbrews.

Beer is popular in Italy, especially with pizza. Just in case you want a change from the national brands here is a map showing the location of the growing number of microbreweries.

http://www.microbirrifici.org/beer_italy_maps.aspx?

Walking around while drinking an individual can of beer is not frowned upon. Walking around while drinking a large bottle or flask of any alcoholic beverage is not well received. "Manifest" (obvious) drunkeness in public is illegal even without alcohol in your hands.