Preferably to the extent that it is implied that they're knowledgeable about the goings on of entertainment.
How about a socialite?
a person who is well known in fashionable society and is fond of social activities and entertainment.
It's not clear what kind of outings you have in mind, but if you're talking about music, most of the time this will suffice:
concertgoer |ˈkänsərtˌgōər| noun a person who attends a concert, esp. one who does so regularly. [NOAD]
This works for classical, rock, jazz and pretty much all kinds of music. It would even work for dance and some other forms of entertainment. But I don't think it extends to all kinds of entertainment: you probably wouldn't use it for, say, puppet shows or jugglers or circuses.
If you love soceity, you would be described as "gregarious"
–adjective 1. fond of the company of others; sociable
The noun for this is "gregarian". So if you love clubs, concerts, bars, and entertainment, you're a "gregarian"
It's reassuring that most answers assumed a social context but it's not essential in this context; particularly since the question emphasized acquiring knowledge but didn't specify an interest in seeking company. There are those who seek music, art. and other forms of entertainment regardless of the social context. In this respect they could be considered aficionados, devotees or enthusiasts. In some (arguably snobbish), instances a person might even claim themselves a student of certain forms of entertainment. Someone describing themselves as a "student of the dance" for instance, pursues experiences that enhance their knowledge and understanding of the particular art form. If their dedication extends beyond "paying admission" to actively supporting or sponsoring the entertainment/art form, they may be referred to as "patrons".
I think a good term for this is social butterfly.
Impresario: (from Italian: impresa, meaning "an enterprise or undertaking") is a person who organizes and often finances concerts, plays or operas; analogous to an artist manager or a film or television producer.
Promoter: An entertainment promoter in industries like music, wrestling, and sports is a person or company in the business of marketing and promoting live events such as concerts/gigs, sports events, professional wrestling (wrestling events), festivals, raves, and nightclubs.
The person who frequents a bar or a restaurant is a patron.