I'm Israeli. I get 3 weeks vacation from work during Sep-Oct 12.
I want to travel overseas (for now alone). I thought to use the relatively long vacation to get further away than nearby Europe. Does anyone know of organized tours for the age of 20-30? (I am 27).
Are the following good to travel alone, at that period of time?
China
Russia
Barcelona + Portugal
Cuba?
These are entirely different classes of travel. Portugal+Spain is an easy trip within the usual Western world, close to home and without any significant apparent dangers other than the usual pickpockets and the expensive Euro zone. You can easily get home if needed (regular flights from Madrid and Barcelona directly to TLV, connections through all around Europe from everywhere else).
Russia, Cuba and China are different kinds of animals.
Russia is an unstable place, other than in the central cities (Moscow, St. Petersburg, provincial capitals, etc) you are in danger. If you go too much south, you'll get to the Muslim areas (Chechnya, Dagestan, Azeri border) where being an Israeli might not be healthy (even relatively to the rest of Russia. They're not big fans). You might not speak the language, you would definitely not know the local way of doing business, and you'll be definitely paying more than a Russian-speaker for everything. Much more. If you stay close to the central places you would be relatively safe, but there were Israelis coming home without fingers from Russia, as you probably know. (FYI for all the haters - lived in Moscow for several years, I know what's going on there from my own experience)
China - same about the language and the cost difference, but (IMHO) much safer for foreign travelers. English spoken in the big cities, talk to younger people (accent may be horrible though...)
Cuba - FAAAAAAAAR. If you go to European parts of Russia, or Portugal+Spain - you can go for a week or two. Going all the way to Cuba (or China) for a week - a huge waste. If you're going for a long time though it might be very interesting, and I would suggest Cuba as the best candidate. It is very unique, and will, likely, disappear (in its current shape) in a decade or two. Once the Castro's are gone, my guess is that Cuba will get back to the close ties with the US it had before, and will change significantly.
September/October is certainly not the best time to visit Cuba, because of the cyclones.
The other three look fine, and can be done alone. Which one to choose is mainly a matter of budget. All else equal, the "Barcelona + Portugal" will be the least costly option.
If I had three weeks and the necessary budget, I would pick Russia and China from your list. More precisely, I would travel on the Trans-Siberian Railway from Moscow to Bejing. Note that this site has some resources on that topic.
I had the best travel experiences, while traveling alone. I can at least confirm that China can be traveled alone. Traveling alone is also the way to meet people. Buy yourself à lonely planet and you'll see that you'll have an instant new social network. You'll keep meeting people you already met in previous visited hostels/hotels/places
I have travelled alone to Cuba, Spain and China and I didn't have any problems in any of those countries. Like the previous answers have stated, Cuba would not be a wise choice for that time of year. Otherwise, that would have been my first choice. Spain and Portugal are easy places to travel in. China, on the other hand was a little more challenging to get around and get myself where I wanted to be purely because of the language barrier.
I would highly recommend, as a solo traveller, to stay in backpackers, no matter where you are. There are loads of other people doing the same thing as you and you get to meet awesome people who can really give you some great tips. And gives you the possibility of doing day trips with other foreigners for those days you want to socialize.
