Public transportation in Vienna is safe and efficient. The network includes buses, streetcars, and subway trains, and a regional train network. The easiest way to navigate and buy tickets is via the WienMobil smartphone app. The weekly ticket is the cheaper option if you will make at least 8 rides. This is the best option for those staying at the Hotel Kaiser Franz Jozef. 

Fare enforcement is by ticket spot checks by plain clothed officials. You must present either an electronic ticket or a validated paper ticket when asked. Riding without a ticket is a €100 fine, with zero tolerance for tourists pleading ignorance.

The standard WienMobil tickets are valid for travel in Zone 1, Wien Kernzone. This is mostly the Vienna city limits. The airport is outside of this zone. To buy a ticket for train travel to or from the airport use the kiosk at the airport or in subway stations, or use the Austrian railways (ÖBB) app. There is also a separate express airport train (City Airport Train) that is 1.4x faster and 3.5x more expensive. 

From the  Hotel Kaiser Franz Jozef  to the ESI: Take streetcar 38 from Sieveringerstraße in the direction Schottentor and get off at Spitalgaße. 

Most of the other hotels are within walking distance to the ESI. 

Please note that due to construction work during the month of July  there is an interruption of subway line U4 between downtown/airport connections and the near North side where the ESI and hotels are located.  This requires one to disembark at Schwedenplatz, take a surface tram to the next subway stop at Schottenring, at which point U4 service resumes.