What is the best way to get to 138, Rambla de Canaletes, Barcelona ( Spain) from Barcelona Int Airport?

I would give the same answer as Sue P cabs are reasonable priced and the quickest way to get around. The airport is a way out of the city so the easiest if you don't know the area is a cab.

Cab. Take a cab. Anything else is too complicated, especially if you only have a day. You need to stroll up the Ramblas...start at one end, and go to the other. While there, you turn off at the Cathedral and stroll through the Barrí Gotic. You might want to stroll up the Passeig de Gracia, and take in some of the architecture, or take a city bus (from Plaça de Catalunya), and get off at La Pedrera. Stroll around the couple of blocks right there. That's really the highlight. Then take a cab to the Sagrada Familia. Actually touring it takes a little while, so you might want to make that for the second day, early. Then, if you think you still have enough time, you might want to go to Parc Güell. Those are the highlights. I suggest, in general, just eat when and where you are hungry. You'll surely find something good. It isn't too hard. Beware, though, the prices for food are pretty reasonable on the Ramblas, but the drinks....THAT's where they get you! And you can't NOT drink, and you can't drink the tap water! Just know that's the killer.