By bus
Buses go from KL to Mid Valley via either Brickfields or Federal Highway.
By train
Although there is a Bangsar station on the Kelana Jaya light rail transit line, it is situated along Jalan Bangsar and not near the restaurant and drinking area of Bangsar Baru. From the station, you'll have to catch buses RapidKL No U87 to get you to Bangsar Baru. This bus also goes past MidValley.
The easiest way to get to Midvalley is to catch a KTM Komuter train to Midvalley station. The station is linked to the Mall via a covered walkway with escalators. The other alternative is to catch an LRT to Bangsar station and transfer onto a Midvalley free shuttle bus which runs every half hour or RapidKL bus No U87/U85/B105/B110 which runs every 30-60 minutes during off-peak hours.