This does not come from the Hitler diaries, it apparently comes from Monologe im Führerhauptquartier, a book grouping notes authored by Hitler and transcriptions of his informal conversations by Heinrich Heim; here is the german text (thanks to redsails for quoting the source).
The part that is of interest here:
Daß der allgemeine Lebensstandard sich gehoben hat, daran ist kein Zweifel. Hunger haben die Menschen nicht gelitten. Alles in allem gesehen, muß man sagen: Die haben Fabriken hier gebaut, wo vor zwei Jahren noch unbekannte Bauerndörfer waren, Fabriken, die die Größe der Hermann-Göring-Werke haben. Sie haben Eisenbahnen, die sind gar nicht eingezeichnet auf der Karte. Bei uns streitet man sich um die Tarife, bevor die Bahn gebaut ist
(copied from the archived book itself just in case, not a third party source)
Google translated:
There is no doubt that the general standard of living has increased. The people did not suffer from hunger. All in all, one has to say: They have built factories here where two years ago there were still unknown farming villages, factories that are the size of the Hermann Göring works. They have railways that aren't even shown on the map. Here we argue about tariffs before the railway is built
It's legit.
See my answer; the quote is legit.