Germany Rail tickets during May, buy there right?

You should have no problem buying a Länder ticket at an automat the morning of your travel. You can buy them ahead of time, but there's no reason to. If you use a ticket counter, they'll charge you an extra €2 for "personal assistance".

For FRA to St.Goar, the standard DB fare is €14,60 pP. Since you would be traveling in several Länder, buying a Länder-Ticket for each Land would cost more, at least for two people. The absolute least expensive way is to buy a local RMV (Rhein-Main-Verkehrsverbund, www.rmv.de) ticket to Bacharach for €9,70and a DB ticket from Bacharach to St. Goar for €3. The total cost would be €12,70 vs €14,60 for the single DB ticket, but I don't know if it would be worth the effort to you.

For St. Goar to Rothenburg, if you purchase in advance on the Bahn website, you can get a Dauer-Spezial fare of €39 per person, €78 for both of you, maybe €29 each. That allows you to ride the express trains, ICE/IC/EC; the trip will take about 6-1/2 hrs. On sat. or sun., you can use a €35 Schönes-Wochenende-Ticket. That only uses regional trains and will take about an hour longer than the express trains and the Dauer fare.

On a weekday, purchase 2 standard fare DB tickets from St. Goar to Kahl(Main) for €42,20 (2 people) and a €27 Bayern-Ticket for Kahl to Rothenburg and use the same trains as with the Schönes-Wochenende-Ticket.

For the rest of the trip, I would just buy Länder tickets from the automats, I've done that perhaps a dozen times without any difficulty.

We are departing St.Goar on Sunday for Rothenburg We'll get them in advance from Hotel internet in order to get an Express train as you stated.

Do you happen to know if there are early Sunday trains out of St.Goar? We have 2 nights in Rothenburg
so we could hop off somehere to break up that trip. I' going to get the mapout and look.

Our FRA arrival is 5am so we have alot of time.
We'll take your suggestion and a buy local RMV and a D ticket in Bacharach. I find that saving here and there like this can keep overall trip costs down or allow us to splurge somewhere else.

Thanks for the great tips and we'll avoid using station booking help unless we're desperate.

Savings fares, eg Dauer-Spezial (unfortunately only in German) or Sparpreis fares, require an express train (ICE/IC/EC) connection, although there can be regional connection(s) at the beginning and destination. There are no starting time limits on Savings fares, just that they must be offered on that connection. Savings fares must be purchased in advance, usually online.

Länder-Tickets, which are offered by the state (as opposed to Federal) run, local train organizations (Land = State, Länder is plural of Land), are only valid on regional trains (IRE/RE/RB/S and some other private companies, like ALX) in that state. Länder-Tickets have a 9 AM weekday limit. Länder-Tickets can be purchased at an automat or ticket counter (€2 extra at the counter), have no advance purchase requirements (so can be purchased the day of travel), and are unlimited (so they don't sell out). Yes, travel time is often longer.

Standard tickets are open tickets, usable on any trains within a time limit (eg 30 days). If you buy reservations (~€4) with standard tickets (only on express trains), they are only valid for that train and expire if you don't use them, but the ticket, itself, is still valid.

Lee:
Do I understand the German rail system correctly?

1. All savings fare tickets regardless of type means that weekday travel must start after 9am, and weekends can start at anytime?

2. I must purchase them (3) days in advance so I need to know my exact travel day and times?

3. Savings fares are mostly limited to Regional trains, meaning travel time is longer.

4. If I use standard fares they cost almost double,
   I can go on any day at any time.