Grab requires an email and phone number to sign up. They send a verification code via SMS so be prepared for that. Cash and credit cards are both accepted on Uber and Grab in Malaysia. Try request shorter trips on Grab instead of Uber, the drivers will be happier due to the incentive structure (i used to drive for both). They are much cheaper than taxi even if a proper taxi meter is used. Taxis around major malls and large hotels avoided. For hotel locations, Le Meridien, Aloft and Hilton is the best for public transport connectivity, The Westin and JW Marriott is opposite a shopping mall (Pavillion KL) that contains also a few bars while Sheraton is kind of far from the more happening places. Bangsar is a nice place in the night too.