It's never quite like an English 'R', because with an English 'R' the tongue does not touch the top of the mouth. However, you do only touch the top of your mouth gently, so it can sound like 'R' - e.g. '알아요' to me sounds more like 'arayo' or even 'adayo' than 'alayo'. When it's followed by another consonant, it can sound more like 'L': 설날 sounds to me like 'sol-lal' and 알겠습니다, 'algessumnida' when you have two ㄹ ㄹ together it's definitely more of an 'L' sound: 몰라요 = 'mollayo' However, this is making it sound too complicated! It's easier to think of it as one sound, 'ㄹ'. Prounounced like an 'L' but your toungue touches the top of your mouth very gently, and slightly further back than 'L'.

Well, I guess almost every 'ㄹ' in Korean is pronounced as 'L'.

If I am not mistaken, we (Korean) don't distinguish "l" and "r" sound in Korean. They both will be translated/pronounced as "ㄹ".