Nice to Genoa by train/bus?

There is an iDBUS that runs between the Nice Airport coach station to the Genoa Principe coach station. Fare is 25Euro. Trip takes 3.0hrs. Not bad. Here's a link to the website. http://www.idbus.com/line/genoa-nice

You can also take the train. You take the SNCF regional train from Nice Ville to Ventimiglia, Italy where you change trains for Genoa. About 20Euro on all regional trains. You can cut the time by about 45 minutes by taking an intercity train from Ventimiglia to Genoa. About 25Euro. On the regional trains, there are no seat reservations. You can just buy your tickets and get on. No discounts either. There are seat reservations on the intercity train and non-refundable discounts but nothing worth trying to purchase early. Just buy these when you get to Nice.

Trying to buy tickets on IDbus and as I can see it is impossible with all my credit cards, I also tried www.capitainetrain.com and it is the same problem, -they are not accept my US credit cards. I called to my banks and they are cleared all security for the purchase, but still I can't buy the tickets. :(

You are too anxious to make sure you have a ticket in your hands. For the train ride, the runs are mostly all regionale trains. Trenitalia won't even sell you such a ticket online unless you are within 7 days of travel. No seat reservations on regionale trains either. They can't be sold out as you can stand if the seats are all taken. It's just like MUNI or BART. Just buy your tickets for the train when you arrive in Nice.

And, why are you trying to use Capitaine Train? I'm not sure that they have ticketing arrangements yet with the Italian train system. The Genova you see on their site may be Geneva, Switzerland. Alternatively, I can see and purchase these tickets on the French SNCF website http://en.voyages-sncf.com right now. You can buy them but you can't print out the tickets at home for the regionale runs. You will have to pick up the tickets at a ticket machine in the train station. Also, if you are looking out more than 90 days, SNCF will not sell you any tickets.

Also, on the SNCF website, they are linked with iDBUS. You can select iDBUS from this website. I've did this but I didn't see any place in the iDBUS website where you enter credit card information. All I saw was that they will send you a confirmation after you fill in the needed information. I didn't proceed further as I didn't want to tie up a bus seat.

Finally, we can be of more help if you will reveal the date when you need to travel.

That bus that takes only 3 hours looks pretty good. Very economical, too. I do want to correct one thing about the trains though. You wouldn't take regional trains all the way, just the one from Nice to Vintimille, the town just over the border in Italy. There you can connect to a train that does require a seat reservation. The trains running directly from Vintimille to Genoa are the #505, 663, 745, 667, 681. I took an intercity on this route many years ago.

I'm not sure which websites you are using, but I looked on the SNCF site, but in the French language. It may show different trains from the English website.

There is no need to buy tickets before you leave home. There has been talk of eliminating the train connection at Ventimiglia, but that does not appear to have happened on the summer schedule.