BahnCard: How to get one Quickly Or Can They be Purchased at a Train Station?

For your short stay in Germany I'd not buy a regular BahnCard but a "Probe-BahnCard", which gives 25% reduction even on saver fares. The price is €19.90 for 3 months. You can order it here (scroll to bottom) and print out it. You will get later a plastic card by mail, that you can simply throw away after your return. Dont forget to cancel the card 6 weeks before expiration at the latest, otherwise you will have to pay for a full year. Cancel it using this form. Select als subject "Kündigung ihrer BahnCard 25" and type in the Bahncard #.

Of course you can buy the card in any DB Reisezentrum as well.

BTW, there is a Probe-BahnCard 50%, too, but it's rather expensive (€79.90)

When you purchased your card, you should have received an email almost immediately with a pdf of the temporary BahnCard that you can use until you receive the physical card in the mail. In the absence of the physical (plastic) card, you can print out the pdf of the temporary card and show that on the train with your ticket and ID. From what I read, you must carry a print-out of the temporary card. They seemed to say you could not show the temporary card on your phone.

My email with the temporary card was titled "Booking confirmation (order ABCDEF)" and I received the physical card (mailed to the US) just over 2 weeks after ordering.

You can also download the DB Navigator app and show the card in the app, but need to take an ID (passport) with you. This option comes with a few restrictions (e.g. outside of Germany, where the train staff may not be able to scan the Bahncard in the app), but works fine on all DB trains within Germany.
Note that you only need the Bahncard for travelling with a discounted ticket, not for buying the ticket.

They seemed to say you could not show the temporary card on your phone.

The DB app will save and show any type of bahncard. But you cannot just save a pdf of any type of BahnCard somewhere else on your phone and use that.

Slight correction to my above post. You can show an electronic copy of the probationary (trial) BahnCard, in the absence of receiving the physical card in the mail.

https://fahrkarten.bahn.de/privatkunde/bahncardbuchen/bahncard_start.post?lang=en&country=GBR&redirected=1&dbkanal_007=L04_S02_D002_KIN0060_PROBE-BAHNCARD-BUCHUNGSBUTTON_LZ03#stay

If you want to make immediate use of a Probe BahnCard, use the booking option here and print out your temporary card at home, or download it as a mobile phone ticket to the DB Navigator on your smartphone. We will post the permanent Probe BahnCard to your home address.

Quick tip for displaying your trial (or regular) BahnCard in the DB Navigator app. When I first installed and logged into the app, the filter was set to display only "valid" cards, i.e., those that were within their validity period - 3 months for the trial card. In the upper right hand corner of the app, select the small funnel icon and uncheck "Only valid" to see your purchased but not-yet-within-its-validity-window card.

Thanks Everyone.

I did get the sample BahnCard for 19.90 EUR and received email on downloading and printing the provisional BahnCard. My issue is that I will likely not receive the official card before I leave on my trip, so I could not figure out from my reading on the DB site, if I will be able to use the provisional card for the 2 weeks I am traveling in Germany. If so, then I will order two more, i.e., for my husband and so. BUT if the provisional card will not be accepted, then it would be a waste of money to purchase these now. So...do you know if the provisional card will be accepted throughout my 2 weeks in Germany?

So...do you know if the provisional card will be accepted throughout my 2 weeks in Germany?

The provisional card is valid for 2 months. It should be printed on the provisional card you already have.

(https://community.bahn.de/questions/1147133-gultigkeitsdauer-probe-bahncard)

If you're bringing a smartphone on your trip, I believe you can view your provisional BahnCard in the app immediately upon purchase, and it is valid for the 3 month period starting from the date of validity that you specified when you purchased the card.

In the app, (register and log in if you haven't already) then tap on the menu (upper left, 3 horizontal lines) and tap "BahnCard" then "My BahnCards." If your card isn't showing already (likely not) then try changing the filter (upper right, funnel icon) to uncheck "Only valid."

If it isn't showing still, you can "add" it like you would a ticket purchase by going back to the menu, choose "My tickets" and then click the + sign in the upper right to enter the order id (from your email) and the surname associated with the card.

Be sure to bring ID to show along with whatever version you show, paper or electronic in the app.