Former Manchester United and England defender Neville was a surprise choice to succeed Nuno Espirito Santo at the stuttering Singapore-owned club after the Portuguese left "by mutual consent" following last weekend's defeat at Sevilla.
Neville will join his brother Phil, an assistant coach, as the business partners of Valencia owner Peter Lim look to put the club back on track after a disappointing run domestically and in Europe.
Valencia last won La Liga in 2004, their sixth Spanish title, and were Champions League runners-up in 2000 and 2001 but have been hobbled since then by financial problems that forced them to sell many of their best players.
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They are severely depleted by injuries and suspensions for Saturday's La Liga game at home to leaders and champions Barcelona before Neville's first game in charge, Wednesday's must-win Champions League game at home to Olympique Lyonnais.
Interim coach Salvador Gonzalez, known as "Voro", told a news conference previewing the Barca game the Nevilles were determined to learn Spanish and Phil could already "stumble through" after arriving in June.
One of the criticisms levelled at the Nevilles' British compatriot David Moyes, who was sacked by Real Sociedad last month, was that he failed to learn Spanish which affected his ability to communicate with the players.
"I don't think that language communication will be a particular problem and in the squad there are quite a few people who have a good level of English," Voro told reporters.
The defeat at Sevilla on Sunday, in which Valencia had two players sent off, left them in ninth place with 19 points from 13 games.
In the Champions League, they face a difficult task to reach the last 16, lying third in Group H with six points from five of six games. Zenit St Petersburg lead with a maximum 15 points, with Ghent on seven.
Voro said Saturday's match at home to Barca would be a stiff test with the Spanish and European champions in superb form.
"We are going to be facing a massive team with brilliant players," he added.
"Despite the number of absentees we will put up a fight. We are confident we can do well and if we manage it will be a huge boost which will help us improve our performances."
(Reporting by Iain Rogers, editing by Ed Osmond)
