Ancestry.com has a death index for California, California Death Index,
1940-1997, and it shows the following:

Karl A. Stieger
Birth Date:     17 Jun 1887
Birthplace:     Switzerland
Death Date:     25 Jun 1969
Death Place:    San Luis Obispo
Mother's Maiden Name:   Stieger

Marie E. Stieger
Birth Date:     28 Jul 1886
Birthplace:     Switzerland
Death Date:     16 Oct 1971
Death Place:    San Luis Obispo

There's a total of 25 people in the death index with the last name of
Stieger.  Some are women, and that's their married name.  Karl and Marie
are the only two who died in the county of San Luis Obispo.

The town that they planned to go to, Taft, is located in Kern County,
California.  San Luis Obispo one of the counties next to it.

The 1930 Federal Census has the couple, but their surname was misspelled
as 'Steager':
Year: 1930; Census Place: Township 7, Kern, California; Roll: 121; Page:
4B; Enumeration District: 40
Steager, Carl, 43, married first at 33, fireman at oil field, born
Switzerland, parents born Switzerland, language spoken at home was
Swiss.  Immigrated 1913, NA
Marie, wife, 43, married first at 33, born Switzerland, parents born
Switzerland, language spoken at home was Swiss, immigrated 1920, AL
Nellie, daughter, 9, born California, parents born Switzerland
Bertam, son, 8, born California, parents born Switzerland
Sarah, daughter, 7, born California, parents born Switzerland
Joseph, son, 4 8/12, born California, parents born Switzerland

(Carl was a Naturalized citizen, Swiss was spoken back home in
Switzerland.  The census indicates that Carl and Marie both spoke English)

The California Birth Index, 1905-1955, at ancestry.com, has the following:

Nellie M. Stieger, born January 22, 1921 in Kern County, CA.  Mother's
maiden name Buschar

Bertraum K. Stieger, born February 7, 1922 in Kern County, CA.  Mother's
maiden name KBushor

Sarah Steigar, born February 26, 1923 in Kern County, CA.  Mother's
maiden name Buchur

Joseph Bedor Stieger, born August 7, 1925 in Kern County, CA.  Mother's
maiden name Bushor

The Ellis Island records do show a Karl Stieger arriving in the U.S. in
1913 and again in 1920, with the ages matching up with a birth year of
1887.

In 1913, Karl was headed to his friend, Otto Zeller, in Henderson, Cal.
  Father Benedik Stieger, residence St. Gellen, Switzerland.  Age 26.
Arrived in the U.S. on September 29, 1913 on the ship La Touraine from
Havre.

In 1920, Karl, aged 33,  was headed to his friend, O. Zeller, Box 327,
Marieopa, Kern, Cal., He had been in the U.S. before, in 1913.  Karl was
5ft. 7inches tall, fair complexion, blonde hair, gray eyes, born in
Altstatten.  Nearest relative in Switzerland was L. Stieger, Kobelwald,
Kt St. Gellen.  Last residence in Switzerland was in Altstatten.
Destination was Taft.

Marie, aged 34, was with him, she was 5feet, 5inches tall, fair
complexion, blonde hair, gray eyes, born in Altstatten.  The rest of her
information is the same as that for Karl.

The ship, the Lapland, arrived in the U.S. on October 23, 1920, out of
Antwerp.

There is an Otto C. Zeller and his family living in Kern County, CA in
the 1930 census.

The birth index for California has an Otto Zeller being born in 1921 in
Kern, with his mother's maiden name Bucher.  However, the 1930 census
does not have a child of that name and age for Otto's household.

Hope that helps,
Cathy