There is a lot of talk about taking the HOHO bus, but I'm wondering if you spend much of the time crawling thru agonizingly slow traffic? If it is anything like London, I'd rather take the Metro. What have others experienced.
I took the Barcelona HOHO last September. If you just want to get quickly from Point A to Point B, take the metro. If you want to see the sites and hear some commentary about what you are seeing, take the HOHO. I do not recall the traffic being agonizingly slow. I suppose it mostly depends on where you are and the time of day.
We enjoyed the HOHO bus, it was a first for us. some of the sites are spread out and they have several routes. did not have an issue with traffic. Beware of pickpockets on the Metro.
We were in Barcelona recently and took the HOHO bus. It was easy and convenient to see the main Gaudi sites. It was safe and easy, and we enjoyed seeing and hearing about other parts of the city that we did not "hop off" to explore. I had ready many warnings (including in the Rick Steves books) about pickpockets on the city busses and Metro in Barcelona.
I took the HOHO bus - not my usual style - because I was traveling with people with mobility issues. The recorded commentary wasn't great, and we did spend some time in traffic, but it's not like I'd imagine London was. Still, it depends on your needs. I prefer to take fast public transit somewhere then walk around to see things. Some people don't like dealing with public transit and just want to see things quickly from a bus. That said, I think that HOHO buses are pretty useless for photography unless you actually get off frequently.
We took the HOHO bus in Barcelona on a Sunday and a Monday, different route each day. On Sunday traffic was no problem, on Monday it was a little worse in some areas but not horrible. While it can be used to get from Point A to Point B the real value for me was getting an overview of the city's different districts, landmarks and major attractions from an elevated vantage point. The ability to hop off then back on later was a plus. The downside of the HOHO bus, besides the expense, is that some of the plugs for the recorded commentary did not work; and the top level can fill up so you have to ride in the lower level with reduced visibility. (asking the driver or ticket person didn't help as they often didn't know if there was room up top). When that is the case you can always hop off at the next stop and wait for a bus with room on top. We found it helpful enough that we decided to ride one again in Madrid.
We are big walkers and we finally succumbed to the lure of the HOHO bus as we were in Barcelona at the end of a 2 week trip and had blisters after logging 10+ miles a day in Copenhagen and Stockholm. Yes the commentary is stale, but dang, did I love this bus because it went some places that aren't easy to get to on the Metro (such as Parc Guell) and it was really relaxing just to sit back and relax. During the middle of the day, we sat inside because the bus had a/c and it was really hot in Barcelona (we were there in the second week of last month). There are 3 loops, the red line is the longest and it takes 2 hours if you sit on it point to point. The other two lines are about 1.5 hours, if memory serves. We hopped off at regular intervals and were quite happy to see buses come within 5-10 minutes of us showing up at a new bus stop. We had a 2 day pass and used it a LOT over those two days. I think it was 24 euros for 1 day and 28 euros for 2 days, or something like that, so we said why not. We also took the metro and walked some as we were there longer than 2 days. I would totally do the HOHO again - I felt it was worth it and it was a nice respite to have a/c in midday heat. As to traffic my husband is from London and I have been there many times. Barcelona traffic doesn't hold a candle to London traffic. It didn't make any impression on me at all, so I don't think it will be a problem. The only negative of the HOHO besides the commentary that is, is that it stops running at 8:30pm. This may seem late, but its not even dark until close to 10pm and that is really when Barcelona gets active again.
We took the HOHO around Barcelona in July. As others have stated, if you just want to get from point A to point B, Metro or taxi is much faster...not because of traffic, but simply because the routes are so long and cover so much territory. We stayed at the Hilton and there was a stop near the hotel for the HOHO. The bus ride to the old Olympic sites (opposite side of town) took a long time because we had to take one bus to the center of town and then another to the sites. It was only a 20 minute taxi ride at most but the HOHO took well over an hour to do. That being said, it was nice to get the tour of the city even if we didn't stop at all of the sights. The commentary is informative as you pass the sights in town.