South of France in 7 days

I'm not sure what you're asking. Go to the train station in Nice. Buy a ticket to Monte Carlo. A train to take you there will be along shortly.

I agree with the previous reply. Some clarification and further information on your question would be very helpful. You can also travel from Nice to Monaco by Bus (fare is only €1 as I recall) and then take another Bus or walk to Monte Carlo. It's a bit of a hike, but certainly possible.

I spent 7 days in 2008 split between Avignon (where I saw the Rhone wine region, Avignon, Nimes, and the Pont du Guard) and Antibes (where I saw Cannes, Antibes, Nice, and Monaco). Easily doable with the frequent local trains and buses.